@@AgentJayZ No worries at all. I fly out of Hilo on the Big Island (former medevac King Air pilot, now flight instructor) so I've been quite interested in this accident. I am a Phormer Phantom Phixer (avionics) so I've really enjoyed your videos on the J79, and your other videos too. Thank you so very much for taking the time and effort to make and post them!
2:48 Bingo!! I seem to remember when this happened, the pilots were down to 99 knots ground speed, and to be that slow, I would expect flaps to be at 15 or so. When the pilots keyed the radio, there was no gear horn.. which you cannot silence at flaps 15, meaning the pilots probably lowered the gear and having flaps and gear out that far out, I would expect the plane can’t hold altitude and possibly the pilots pushed up the only remaining engine to the point of failure. (All speculation, although I have time in this exact tail number.) IMO, the better way to deal with this was just put the gear down and turn base and land.. not go out 20 miles! If they really wanted to go out 20 miles, and run the checklists, climb it up to 5,000 or so.. this way you can configure flaps and gear on the glide slope instead of at 2000 feet on a straight and level segment.
15:05 this plane did NOT have a FADAC. On planes that I’ve flown with FADAC, (737 NG, CRJ 700&900) they do have a way to turn it off via a guarded switch..
As a fyi there is no FADEC on a 737-200 (controls remain as designed 40+ years ago) ... something else to consider in this case, the airline in question was investigated and almost immediately grounded for ... let's just call it "shady maintenance practices" One would presume there will be additional illumination on that when the final report comes out. Also, unbelievably, in this particular crash, both pilots crawled out of the sinking fuselage (the forward part snapped off and separated from the wings/aft on impact) and were rescued. Two very lucky guys.
The aircraft wreckage, Cockpit Voice Recorder, Flight Data Recorder and both engines were recovered. We just have to wait for the NTSB investigation to be completed.
Great video, and I admire that you just went with answering the questions without having researched the accident in question. JT8D engines do not have a FADEC, but rather a hydromechanical fuel control unit, so they can pretty much keep pumping more fuel in until the over speed governor kicks in. Anyhow, I believe that in this instance, the pilots pulled back power on the wrong engine and tried to continue flight on the failing engine. 🤦♂️
It was Transair Flight 810. Only one engine failed due to turbine blade failure but confusion amongst the pilots caused a misdiagnoses of which engine failed. End result was overtaxing the already damaged engine. Check out Mentour Pilot's channel for the full story.
You are almost correct on the FADEC part without a cheat mode. MD-11 is the weird one out here, it had an "overboost" bar at the end of the throttles, that allows you to get a bit extra performance out of the engines in emergencies, such as stall recovery, which is what the manual mentions it for. But where you are almost correct part is that the FADEC is still in control, but when that bar is tripped, it switches the FADEC to alternate mode where it operates in degraded operation and a bit less parameters. The side effect is that it gives you 5-10% extra power for a limited amount of time. But the FADEC is still in control of the engine, so you are correct in that part.
Sitting at LHR, with a glass of red wine, waiting for bag drop for my flight to SG to open. I'm on a B.777, but it's good to see BA's A380s back in service. Nothing to beat them, in terms of passenger experience.
I know a thing or two about accident investigation/analysis, and basically the only cases where two engines fail (almost) at the same time without external causes, is fuel exhaustion, or, if one engines fails, and the crew erroneously shuts down the good engine (this happens more often that you might think and has led to fatal crashes). There are, of course, external factors that may cause this, such as bird strikes (Hudson River "Miracle"), volcanic ash, or extremely severe precipitation, but I don't think either was the case here. Some fuel systems (we looked at that in some detail ofter the BA38 crash landing in Heathrow, the case with the fuel/oil heat exchanger accumulating ice) intentionally stir the fuel with recirculation jet pumps to keep water suspended in fine droplets instead of accumulating at low points in the tanks. The engine just eats finely suspended water without any problem. It's just large continuous globs of water which would cause a flameout.
A possible factor, the engines were not 'airworthy' and the airline was shut down for multiple safety failures inc 33 flights without airworthy engines.
Bad fuel can lead to (dual) engine problems, there was an A330 which had filter/absorber material in its fuel and this messed with the fuel metering unit of the engines, causing engine stalls. There also was an incident with an A321 I believe, where the fuel was mixed with way too much antibiological agent to keep the tanks clean, which also caused issues with the fuel control and engine surges, leading to the need of changing both engines and the APU.
Love your channel and I'm an A and P mechanic and if I ever had to completely refurbish a turbine engine you would be my guy to do it. You are meticulous in your work and it clearly shows. Regarding 45's aircraft, it wasn't the engines, it was the nose cowl rings. They were due for overhaul. They sent them to a shop to be overhauled. They were the only ones in the shop at that time for Rolls Royce engines. His aircraft has low time on the airframe and the components, most original with the aircraft. They made a big to do because they didn't want to amend the paperwork because the aircraft was scheduled to go back into service in a short time. Regarding the JT8D engine, trained on this engine. Wasn't a powerhouse like the CFM engines but it was reliable and could take the abuse of continuous airline ops. If you want to see them scream, check out the older youtube videos on the md-80s taking off from St. Barts next to the beach...
Regarding water in the fuel tanks, each tank has a small drain valve (either petcock or poppet valve)at the lowest point of the tank that is supposed to be opened to allow sample to be drained into a container so it can be inspected for water since water will settle below the fuel. Problem is, it takes hours for the water to settle out after refueling and most airliners are fuelled shortly before each flight so if a sample is taken the water is still suspended in the fuel.
I suspect that the concern about water in the fuel might go back to the event in January 2003, when BA38 crash-landed short of the runway at LHR. It might well have ended up as a smoking wreck in Hounslow, but for the the instinctive and commendable actions of Captain Burkill. However, the event was very unusual and caused by the flight from Beijing having experienced unusually low temperatures high over Siberia. Extensive rig testing subsequently proved that water in the fuel formed ice on the walls of the pipework during the flight, which was released as the temperature increased during the descent. The resultant 'slush' clogged up the entry to the fuel tubes in the fuel-oil heat exchangers (FOHEs), which restricted fuel flow to the engines. It was nothing to do with water affecting the combustion process. Even relatively greater amounts of water suspended in the fuel, provided that it was dispersed, would have had a negligible effect on combustion. The FOHE used on the Trent 800 (and other Trent engines) was subsequently subject to a relatively minor redesign, to minimise the likelihood of a recurrence. Nevertheless, with the possibility of unusually low temperatures at cruise altitudes having been recognised, the risk of future events could probably have been minimised quite safely by means of changes to the flight profile on descent. I am reminded of the intake icing problems encountered by the Proteus turboprop engines of the Bristol Britannia in the early 1950s, during flight trials over Africa. Under certain conditions at altitude in the Tropics, ice would build up in the bends of the engine intake duct and be released as a large 'slug' into the compressor. The sudden ingestion of a large amount of water certainly did result in an engine flameout. However, it was rapidly established that the phenomenon could be anticipated by identifying the atmospheric conditions, and all that was needed to ensure the engines relit was to switch the engine igniters on beforehand. Nevertheless, with the Comet disasters still fresh in the minds of both the industry and the flying public, BOAC demanded design changes to overcome the problem, delaying entry into service of the Britannia by two years.
Juan has two videos about the ditching. I would assume there will be another one when the final report comes out. They kept flying out to sea while doing checklists instead of turning back immediately.
Possibility for shutting down the wrong engine after the left engine failed; N2 drops into windmill range before error is discovered, say 15 seconds...now below the 250 kt windmill minimum start airspeed, the restart attempt goes hot (compressor hung stall) and she sits there at 30-40% with progressivley increasing EGT - interpreted as 'hot'. Almost no thrust in that condition, below idle.
Hey, really good explanation for that phenomenon, I was wondering what those flags on the wall suppose to represent? Which do you have, it's seems that there are a lot of flags!
Your point about the airframe and engines having different lifecycles got me thinking. Is there anything not related to damage that prevents another overhaul of an engine? Airframes have a cycle number limit due to metal fatigue. Is there any similar restriction in engines or are they essentially infinitely rebuildable if they don’t suffer catastrophic damage? Thanks.
Certain parts, like bearings, turbine discs and blades, may have a life limitation specified in hours, or in number of cycles. The external accessories like fuel pumps, valves, oil pumps will all have there own specified replacement of overhaul schedules. But things like cases, shafts, and stators can live forever, providing they pass inspection at each overhaul. Everything eventually wears out, but many aircraft engines are still serviceable or repairable after the particular air frame they are designed for is retired, so they have little value at that time. In my videos called turbofan parts donor, we take parts out of a CF6-6 to use in rebuilding a damaged LM2500. Those are the air and ground versions of the same core engine. The CF6 was sold for scrap, because it was used in the A-300. It contained many parts that were serviceable, and that 2500 is running today.
just finished watch this recorded video you presented. good work ! be good to eventually know time line and reason for failures. I hope my prior question not a dumb one, just think that aspect of a jet engine not discussed or no need for discussion or a question not asked before. Curious , you show jet engine operation at ground level but a comparison at high altitude I think be interesting content. Mike just curious
Carrot Top Pres insisted on Rolls Royce engines for his 757 ( I believe they used RR RB211's, not really sure, not too familiar with this airframe) but even on his aircraft the engines were leased from a company specializing in engines. When his aircraft was grounded during his tenure in office the engines were removed and returned to the leasing company to eliminate extra costs to his corporation for the four years he was in office. Just like having a grounded aircraft not making money, the same applies to engines, they belong to the leasing company and they must continue to make money. Just think of the cost to tear down and inspect these engines before placing them into the engine pool to continue making money for the company.
I've taken some pleasure in telling American contributors to this channel on more than one occasion that Trump Force One had Rolls-Royce engines (never forget the hyphen: its omission is a capital offence). The engines would be RB211-535s and, having looked at a few shots of the aircraft, I think that they are -535E4s, with hollow, wide-chord fan blades. I've also taken pleasure in stating that the -535 was the first large turbofan engine to achieve over 40,000 hours 'on the wing'. In its day, it was the most reliable large civil turbofan of any in service at the time. However, I wasn't aware The Donald had actually specified that he wanted a 757 with Rolls-Royce engines. I believe that the aircraft started life in airline service and changed hands a couple of times before it was converted into a big executive jet. I had assumed that the aircraft came on the market at the right time and his organisation bought it.
always love your work and knowledge, I am an old private pilot. I have a question, I know turbochargers spin faster in thinner air, allowing performance to be maintained. aircraft jet engines same but what is the rpm increase say at higher altitude vs ground level test cell rpm ? Mike curious follower
In a less dense atmosphere, the HP system of a two spool turbofan will spin at its nominal speed, because it is essentially turbocharged by the LP system, which will spin faster at higher altitudes.
Hi, I was a Royal Air Force aircraft engine tech. I worked in various engine shops on RR Avon, Orpheus, Gnome, Spey etc. I’m quite surprised that you don’t seem to have your components blanked off, to stop crap entering?
In this video, all parts are scrap, for demo puposes only. Anything we use is cleaned and inspected immediately before installation, then covered while awaiting the next bit.
Compressor and turbine discs (and possibly some mainshafts) are typically designed to have a Predicted Safe Cyclic Life (PSCL). When a new design of engine released to service, the discs will be restricted to a proportion ((say a quarter) of the PSCL, at which time the discs must be inspected and, if satisfactory, they will be released for further service. Their lives will then be progressively extended with further inspections until they achieve their PSCL. On occasions, shortcomings in the original design may detected by these periodic inspections, which will mean that the PSCL will not be achieved. In such cases, the disc life will be limited and a revised design may be required. In practice, during the early life of a new type of engine, other components (eg, combustion chambers and HP turbine NGVs and blades) may need to be replaced or repaired, allowing more frequent inspections of the discs.
I love your channel. Question, have you ever used or addressed ceramic ball bearings? Are they using them in helicopter engine? I think they are. They create no heat? No oil? Thanks.
Never heard of them being used. No such thing as a perfect bearing. The deflection which causes heat happens in the race, too. Ceramic rollers, and ceramic races? Never heard of that.
A little googling brought up a few articles saying SKF are supplying the hybrid ceramic main bearings for the CFM LEAP, i couldnt confirm if this made it into final manufacturing but it was part of the design frozen for flight testing
I actually heard that a lot of airlines buy the aircraft or airframe and lease the engines out of a leasing pool. So it's cheaper if an engine malfunctions they get another engine.
All engines in all airliners are simply modules, and replaced whenever needed. That's the way it works. A "numbers matching airframe and engines" is not a thing. These are not cars, or motorbikes. The airframe and the engines have totally separate careers.
General aviation is an entirely different universe of laws and regulations. The owners have the option of an exchange engine within a few days, or many weeks for the original to be overhauled. I guess airlines have the same option, but those aircraft cost hundreds of millions, and make millions per day. Every day out of service costs big money.
While I don't know the details particularly of this aircraft, that carrier had a reputation for let's just say not keeping up with maintenance. They were cargo outfit. I believe the airline is gone now
These discussions have taken me back to the crash-landing of BA38 at LHR in 2008 and the crash of British Midland flight BD092 onto the M1 in 1989. They have also encouraged me to buy two more books on aviation disasters, to add to my small collection of such books. My interests are in what went wrong and what lessons there are to be learned. I am now reading 'Flight failure' by Donald J Porter, in which he investigates "the nuts and bolts 0f air disasters" - quite literally. His description of the omission of cotter pins from elevator control rods, resulting in fatal crashes and an aborted take-off that would otherwise have been fatal, was quite chilling. It was particularly so because of a first-hand experience, which I think I may have mentioned on this channel in the past. In the latter stages of my career, I was tasked with a redesign, the objective of which was to eliminate the need for the use of cotter pins at 42 positions in a complex mechanism. The omission (or the failure to bend the 'legs') of a pin had nearly resulted in the loss of a single-engined fighter aircraft, which managed to make a fast, fixed-throttle landing. Now, at risk stirring up a debate, I must comment on yet another difference in engineering terminology between this side of the pond and N America. I have used the term 'cotter pin', as used in the book, so that North American readers recognise the simple piece of bent steel in question. However, on this side of the pond, we would more commonly call it a split pin - although N American terminology has, inevitably, crept in, is understood and even used interchangeably. Nevertheless, I was brought up to call the pin that fixed a bike pedal crank to the chainwheel shaft a cotter pin, together with pins in similar applications on, for example, steam locomotive motions.
@@AgentJayZ The other book, which I have yet to begin reading, is, 'The Mammoth Book of Air Disasters and Near Misses', by Paul Simpson. First published in the UK, it has also been published in the USA. Personally, I find the title rather inappropriate for such a serious subject, as it sounds rather like that of a child's story book. The other books I would strongly recommend are, ''Air Disaster: Volumes 1 to 4', by Macarthur Job. However, these appear to be long out of print, but may be available on Kindle. PS I also have books on railway disasters in the UK. My interest was quite possibly initiated by the childhood memory I've mentioned elsewhere, plus the fact that I was brought up in a house overlooking the West Coast main line between London and Glasgow.
@AgentJayZ PS I came up with a really foolproof redesign, which eliminated the need for split/cotter pins. However, I readily admit that it was an adaptation of something I'd seen in the linkage on a helicopter engine. Some French designer had come up with a really great idea. My design proposal and report were forwarded to the USMC, who would have had to foot the bill for the modification. However, having asked for a redesign, they declined it on the grounds of cost, deciding instead to rely on more rigorous inspection.
@AgentJayZ I thought better of bringing the second book about air disasters for reading on the flight to Singapore I could happily sit there reading it, but other pax might get worried if they read the cover.
I was working for BM at that time, training as an avionic workshop technician ( repairing avionic equipment in a newly built clean room environment). My workshop was attached ti the side of the hanger and I would walk through the hanger (EMA) to the locker where I kept my motorcycle gear. I remember vividly a palpable sense of a shocked workforce on the Monday morning, I was in the pub on a Friday when it crashed and I assumed it must have been one of the aging DC9’s we were flying, the 737 was brand new so it was all the more shocking! A few days later I arrived at work to find another brand new 737 sitting in the hanger, as I wandered past it I peered into one of the engines to see a missing fan blade and a very smashed up CFM-56 front fan!!!! The exact same failure had occurred again only this time the crew had shut down the correct engine and landed safely. The 737-400 was grounded a few days later until the issue was sorted out, sadly too late for the poor souls that perished on that terrible evening. I believe it turned out to be vibration at certain points during the climb that caused a fatigue failure of the front fan blades?
Am very interested in your thoughts of the Quantas flight 32 A380 had a massive turbine failure? I'm interested in hearing your opinions on this situation
As I see it, the failure of two engines, within a few moments of each other, is most commonly due to either fuel exhaustion, for whatever reason. Eg, empty tanks, mismanaged fuel system or some mechanical damage to the fuel system. Alternately, as the incident with Sully & his ditching in the Hudson has shown, a double failure could be caused by the ingestion of material that causes serious engine damage, such as a flock of birds, or perhaps ingestion of volcanic ash in the vicinity of a volcano. I'm pretty sure that a dual flame out on an airliner in flight is down to a version of one or both of these two scenarios, but overall, the chances of this happening are pretty damn remote.
New subscriber, sorry, I haven't viewed all your previous videos so the answer to my question may lie in your back catalogue. Re compression ratios and altitude. At altitude atmospheric pressure is considerably lower than at sea level. Does the turbine compensate for this, or does power drop off with increasing altitude? Thanks
Compressor outlet does depend on inlet air density, so all engines are tested under standard conditions. 59 degrees F and sea level altitude. If test conditions differ, adjustment calculations are made.
Sorry, but you have made the elementary error of using the term "compression ratio", which is the volume ratio of a piston engine, ie, the total cylinder volume at BDC divided by the volume at TDC. Pressure ratio is the correct term for a gas turbine engine, ie, the pressure at compressor delivery divided by the pressure at compressor inlet. The pressure ratio of a jet engine compressor remains approximately constant at a given rotational speed. In other words, the lower the inlet pressure, the lower the compressor delivery pressure. Power/thrust drops off with increasing altitude, as a result of the reducing density of the air - but so does the aerodynamic drag on the aircraft, so that less thrust is required. The example I have quoted many times in the past is the RB211-22B in the Tristar. At T/O the thrust was 42,000lb., but at cruise (520 knots at 35,000ft) the thrust was around 9,000lb.
The main engine casing and maybe the disc rotors and shafts. I don't think that the compressor and turbine blades will make it that long, bearings are likely changed several times.
I am curious as to what part of the engine is the part that contains the serial number that IS that engine? As an example, The lower receiver an an AR-15 is the only thing that has a serial number on it that has to be registered. IF something happens to that receiver and it has to be replaced then it becomes a different gun. What part of the jet engine is the "lower receiver"?
The engine is identified by a brass or stainless steel data plate attached usually somewhere on the front frame, but the front frame is a replaceable module. If a front frame gets replaced, the data plate is moved to it, and the engine keeps the same serial number. With the Orenda 14, I have replaced every single part in various overhauls, and there is no single identifying part, other than the data plate. Kind of a philosophical question you have posed. Usually an engine will be repaired or determined to be "beyond economical repair". Serviceable engines for Sabre jets are rare, and so the term "economical" is bumped a little higher these days.
Hey AgentJayZ. Funny you mentioned Juan Brown's Bloncolirio 'cause I've always saw you like the "Juan Brown" of aircraft engines, if you allow me the comparison. I mean his field of expertise is obviously airplanes in itself and what can be the cause of some reason behind an event, as yours is undoubtedly what makes them fly. Greetings from Portugal
Gotta be careful with that username. Somebody else owns it, and if my channel was taken down... wouldn't that be crappy? Thanks for the nice words, but can you fix that?
@@AgentJayZ Didn't know someone else used the same nickname. I've been using it for ages, and my comments are always straight, polite and respectful. But if you care I can tell you that behind this nickname is a Miguel from Portugal. Best regards.
It would make me feel much more secure if you could address me as AgentJayZ. Even that is pretty close to a certain billionaire, who has left me alone so far. If you don't know of him, that's OK, because I had never heard of him either when I came up with my username. But I don't want to get into a dispute with his lawyers. Editing a comment is very easy, and I thank you for considering it.
@@AgentJayZ Ok. No problem AgentJayZ. I thought you were referring to my "nickname". Oh! And keep on doing the nice work. It's always good to hear someone talk about a subject (aircraft engines in this case) the way you do. Best regards.
Obviously you rebuild/repair these engines back to manufacturers specifications/tolerances, and you've mentioned several times you are "simply" (not trying to imply this is simple/easy) the technician performing the work as detailed by the engineers who designed these amazing engines... however, in your experience over all these years, have you had (or come across) any changes/modifications/improvements that would make these engines more efficient/reliable from their original design? For example, if you had an LM1500/2500 of your own, what changes/upgrades/improvements would you make beyond the original design?
Don't try to be an engine designer unless you've really got it. And when optimizing an existing engine, there are two ways to do it: let it make more power or let it make the same power while burning less fuel. Or maybe three ways when you're interested about environmental impacts, let it burn "cleaner". Changes you can make to an existing engine would be installing other compressor and/or turbine blades (and their corresponding stators), combustor(s) and maybe changes allowing higher 1st stage turbine inlet temperatures, which are usually the main limiting factor for turbine engine power.
Storm is incorrect. You can't use different parts. What you can do, and what we do here in FSJ, is have ceramic coatings applied to the parts exposed to heat. This is not for performance increase, but to add greatly to the longevity of the coated parts. Designing upgraded parts is far above anybody's capability besides the engine manufacturer, and swapping in parts from other engine types (even if they would fit, which they won't) is nothing but foolish gambling.
One example of an engine that was improved from its original design, which AgentJayZ has come across, is the 'C' rated Industrial Olympus (aka 2020 series) engine that he has shown us several times over the years. The improvements were designed, tested and produced by the Industrial and Marine Division of Rolls-Royce - and could only have been done by R-R. The original engine was the Olympus 200 series aero engine, as used in the Avro Vulcan delta-winged bomber. However, the aero engine needed improvements to make it reliable enough for industrial and marine use, because of the higher loads to which it would subjected when operating exclusively at ground/sea level. The initial standard of Industrial/Marine Olympus was the 'A' rated version, which was soon uprated to the 'B' rated version: this was rated at 17.5 to 20MW in industrial applications. The Marine Olympus engine that AgentJayZ showed us on test recently would have been 'B' rated, with a maximum power of 27,250SHP at the power turbine output shaft coupling. Unfortunately, at this distance in time, I can't tell you in detail what the design changes were, but they were relatively minor, as compared to the 'C' rated engine that followed. Typically, any Magnesium casings would have been replaced with Aluminium, and I recall that the all-Aluminium LP compressor rotor of the aero engine was changed to steel, and both the LP and HP thrust bearings were enlarged, to take the higher thrust loads. The Olympus 'C' engine, rated at 30MW, was designed between 1971 and 1972. Relative to the 'B' rated engine, it had a major redesign of the eight combustion chambers, to cope with the higher turbine entry temperature: the design changes were based on the combustion chambers of an early development standard of the Concorde engine. The Olympus 'C' had a completely new design of HP turbine with cooled NGVs and blades, followed by an LP turbine with improved materials and aerodynamics. How do I know all this? Because, as a young designer, I designed the LP turbine blade for the Olympus 'C'.
@@mbunds The process has been applied reliably for decades now. Any airliner you fly in these days will almost certainly have TBC on the HP turbine NGVs and blades in its engines - and elsewhere as necessary.
I have an interest in aviation and mechanics. I would love to know if the throttle controls are directly attached to the engine? i.e Is there an ECU between the engine and operator? Also, what is responsible for handling the thrust? is it ball bearing or hydrostatic?
All modern engines have a Full Authority Digital Engine Control, or FADEC, which operates the engine. The pilot communicates with the FADEC. The old 1950s fighter jet engines I work on use a main fuel control that is a hydromechanical analog computer, and it makes adjustments for engine speed and temperature, altitude, air temp, and pilot input. The only time a pilot has direct control over the engine is when these old jets are switched to emergency fuel control. It is then very easy to burn up an engine. There is no manual override on modern airliner engines.
Where the thrust comes from is a dark mystery hidden in the depths of magic multiplied by mathematical suspicion and engineering clairvoyance. For a single shaft turbojet without an afterburner : ... Most of the thrust comes from the final accelerating "jet" nozzle, which is simply a narrowing of the exhaust outlet. Everything upstream of the nozzle... the whole engine, really, is a device for creating the hot gas stream that the nozzle squirts out the back to create the thrust. The entire jet engine, without the accelerating nozzle, is technically called a gas generator. The addition of the narrowing, gas accelerating "jet" nozzle is what turns a gas generator into a turbojet engine. So the thrust pushes everything forward. It acts on the cases, the combustor liners and their cases, the turbine, even the compressor. All of that is transferred to the outer engine cases, and they are attached to the aircraft by the main engine mounts. Other than that, it's all magic. Graham is our resident Gas Turbine Design Engineer. I hope he sees this and gives his assessment of how right and wrong I am here.
@@AgentJayZ Thanks for the great info and for replying but I was thinking about the thrust on the main shaft. i.e. on a piston-engined car there is a thrust bearing on the crankshaft which usually isn't under much load until the clutch is pressed but on a jet engine, I would expect quite a considerable load on the main shaft i.e. the shaft is compressing the air and is thus trying come out the front of the engine. I'd like to think clairvoyance is the answer or magical pixies are holding it back but that doesn't seem quite right as I can't find any part numbers for them.🤣
@@MrMaxeemum You are obviously thinking about the the huge forward load on the compressor rotor, which contributes a proportion of the increase in pressure (a greater proportion is actually contributed by the stationary vanes of the compressor). However, you have obviously not thought about the (almost as) huge rearward load produced by the turbine rotor. The nett load on the thrust bearing (aka the location bearing) is the relatively small difference between these two huge loads, which is still quite a large load. In an engine the size of the Orenda, it could amount to several thousands of pounds of force. However, there are various methods of reducing the thrust load on the bearing, using a so-called thrust balance piston. For, example, high pressure air can be applied to the front of the compressor rotor, or the rear of the rotor can be vented to atmosphere or to a low pressure region elsewhere in the engine. In aero gas turbine engines (and their industrial/marine derivatives), the mainshaft bearings are exclusively rolling element bearings, ie, roller bearings and ball bearings. However, the 'heavyweight' industrial gas turbine engines typically have hydrodynamic (not hydrostatic) bearings. The journal bearings may be 'plain' bearings but, in some cases, could possibly be tilting pad journal bearings., while the thrust bearings are most probably tilting pad bearings. I readily admit that they are not part of my experience: I am going on what I have seen in cross sectional drawings and other illustrations.
me again, Mike. maybe if my question something you want to discuss, include how fuel is controlled as rpm increases and how there is a max altitude air density and is engine limited at thin air conditions, sensors ? computers ? Just curious. Mike
The main fuel control, which is the analogue device that was replaced in the 70's by FADEC, is a hugely complicated thing that uses inputs from sensors for air temp, inlet air pressure, compressor discharge pressure, engine rpm, exhaust gas temp, pilot throttle input, airspeed. Any of the introductory text books, such as the ones I recommend in my video called "Books" will devote an entire chapter on engine controls. I've just reached the limit of what I can explain in a comment box.
Hello agent I have a question that has not been solved concerning speedbird 009 Captain Eric moody in June 1982 without radar contact flew through a volcanic ash cloud losing all four engines from a 747 200 Rolls Royce RB211 with Ash liquefying choking engines he says he made between 30 and 50 Relight attempts and all worked out in the end my question being the APU was breathing the same air, The batteries had to be good Was the RAM air turbine deployed? Your technical opinion would be greatly appreciated. My favourite aviation story. With st. Elmo's Fire and a story That Ends Well, How are you I hope all is good Mic stone
I must be one of the few people still around who actually saw components from one of G-BDXH's engines at Derby, following the infamous event on 24 June 1982. As I recall, there was significant erosion of the compressor blading and evidence of the deposition of ash in the compressors. In passing through the combustion chamber flame, the ash would have melted, to be deposited like a layer of glass on the HP turbine aerofoils. The degradation of the turbine aerodynamics was probably the biggest single contributor to the overall performance degradation of the engines. This, combined with the degradation of the compressors, resulted in all four engines surging and flaming out. Fortunately, as the turbine blades and vanes cooled, the 'glass' deposits tended to spall off and restore the turbine aerodynamics to some extent. Similarly, some of the ash deposits in the compressors would have become dislodged, allowing the compressor aerodynamics also to be restored to some extent. I've tried the AAIB website for a report on the incident, but nothing comes up. A source of information, which I immediately have to hand, is Macarthur Job's book, 'Air Disaster, Volume 2': however, I think that it is now out of print, but it is available on Kindle. Job's account makes no mention of the APU being powered up: he refers to battery power being supplied by an emergency inverter to the standby busbar. In any case, with the APU in the tail of a 747, if it had been started, it would not necessarily have been breathing "the same air": the concentration of ash could well have been less, relative to the engines. Furthermore, if it had been started in response to the emergency, it would have been 'clean', relative to four already badly contaminated and degraded RB211s. You ask about the ram air turbine: however, I believe I've read somewhere that the only 747 to have a RAT is the last model, the 747-8. What exactly did you have in mind in terms of a technical opinion?
The RAT's are primarily found on most all of the Airbus aircraft. Boeing in all of its 747 production runs up to the -400 series never had these devices. I have never heard of or read anywhere as to their use on 777 or 787 series of aircraft. They are an excellent idea but I wonder if they could be economically refit to older airframes considering the whole aircraft would have to be re-certified if the FAA could come up with a feasible plan to do so.
747 have never had a RAT or Ram Air Turbine until the 747-8 was made, their reliance on making electric power was by windmilling the 4 engines up to and including the 747-400. The upgraded and semi fly by wire setup for the -8 warranted installation of a RAT. Also starting an APU at high altitude is problematic and not reliable, so instead the relight procedure relies on changing the speed of the aircraft by trading altitude for speed.
The fuel thing reminds me of the Dan Cooper conspiracy theories -- "Why did the plane have enough fuel to circle for three hours on what was intended to be a 30-minute hop?" Maybe the plane was supposed to offload passengers, bring on new pax, and go somewhere else after landing at SEATAC?
There is an FAA requirement for a passenger aircraft to carry sufficient fuel for the flight (A to B) plus a reserve of at least 30 (or is it 60?) minutes. The flight from B to C is a new flight and so it will have to depart with enough fuel for that flight, plus the required reserve.
Could be fuel "tankering". Fuel is significantly cheaper at the starting airport that it is cost effective enough to take on enough fuel so the plane can go to its destination and come back in addition to the fueling that covers alternate airport trip time and the minimum extra 30 minute requirements.
Aircraft that are operating on 'long hop' routes will frequently fill up with enough fuel to fly all of their scheduled legs, with a reserve cushion for the last leg. Of course that's assuming that fuel prices are the same everywhere, and the plane has sufficient fuel capacity to do so.
Those engines had quite a career... No 1: 32.3k hours, 33.7k cycles, manufactured 1971-06-24. No 2: 70.8k hours, 101.4k cycles, manufactured 1968-01-10.
The engine behind me has about 2500 hours on it since new, and was last overhauled by me in 2012, before that it was 1960. The build date is not recorded, but probably in the early 1950s.
@@AgentJayZ 2500 hours? so it's basically new? ;-) The 100k cycles on the no 2 engine seems like a lot though... that's an average of 5 flights per day for 55 years.
So long as maintenance is kept up, many cycles can be accumulated without problem. I just read the pre-lim report on this incident, and the engines were described as non-airworthy, so I wonder what that means... My engines have usually come from decades of poor storage, and suffer damage due to corrosion.
@@AgentJayZ Yeah the powerplants group report on the NTSB docket pins the no 2 engine failure on a HP turbine blade fracture, "It was determined that the most probable failure mode was internal oxidation/corrosion that led to the loss of load-bearing cross section, resulting in stress rupture fracture"
@@AgentJayZ according to the wikipedia on transair "On May 25, 2022, citing numerous safety violations found during its investigation of Flight 810, the FAA announced that it is revoking Rhoades' air operator's certificate. Among the cited violations were 33 flights undertaken with engines that were not airworthy. Rhoades was given until June 8 to appeal the agency's decision." I presume this means they were operating beyond maintenance/overhaul schedule?
Aircraft are machines. I think I know what you might be asking, but I no longer make those kind of guesses. I think you need to be more specific with your question.
If you mean, to take a current example, can an Airbus A320 neo, fitted with CFM LEAP engines, simply have them replaced with P&W GTF engines, as part of a routine maintenance procedure, the answer is no. The aircraft would have been designed to have either one engine type or the other fitted as new, but not for interchangeability during service. If it were possible, then some airlines might be trying to fit LEAP engines in place of GTFs right now. There are numerous examples of engine options being offered by aircraft manufactures over the decades. For Instance, the 747 has flown with P&W, GE and Rolls-Royce engines, the 757 with P&W and R-R engines, the 777 with GE and R-R engines, the 787 with GE and R-R engines, to name but a few examples.
Yes. 1500 hours. Certain modules have longer intervals. On the fan module of the GE 90, the overhaul interval is 50,000 hrs. Much longer than the engine core.
Completely different, but the Aprilia RSV/SXV550 v-twin engine has an overhaul time of 90 hours. Top fuel dragsters have an overhaul time in seconds XD
oh man you really should not disclose you get email for every comment question: has any aircraft jet ever utilized an intercooler like in industrial applications(albeit would have to be very compact)?
If you mean an intercooler aft of the compressor, why would you want to toss all that energy, when it could help drive the turbine? OTOH, with a turbocharged Otto-cycle recip, elevated charge temp would not result in more power out, but would put more stress on the bottom end, and make detonation more likely. Good idea to keep temps within limits there.
Jet engines are all about thermal efficiency. The turbine is driven by heat and pressure, (i.e. after each turbine stage the pressure is lower, and the exhaust is notably cooler than it was before the stage) If youre talking equivalent to a car intercooler,. i.e. taking heat out out pre-combustion to increase air density, You would just be taking heat energy that you paid to produce and throwing it away. In a car engine, youre using an intercooler to control knock/preignition, and to limit peak EGTs. Being able to fit more air in the combustion chamber at the same boost pressure happens, yes, but you could fit the same amount of air with just more boost. But that doesnt work if youre knocking, so intercoolers get used to deal with that. Back to jet engines though There is no concerns over pre-ignition with the flame being continuous, so EGT/ Turbine temps are the limiting factor then. Taking cooling air from the compressor and letting it blow over components that need it post-combustion takes care of the other benefit an intercooler could theoretically provide, making it not even something to consider. In general, more pressure and more heat increases thermal efficiency in jet engines. Thats why they are looking to still improve turbine materials, to use less and less bleed air to make more and more efficient jet engines.
@@CKOD Unfortunately, your comment is misinformed. Your familiarity with intercooler applications in piston engines does not mean much when it comes to turbines. It absolutely can be beneficial to use an intercooler between the LPC and HPC sections, and if the engine cycle parameters are suitable, it will increase the efficiency of the engine when combined with a recuperator. Case in point - the Rolls Royce WR-21 uses an intercooler and a recuperator, and achieves efficiency well above what typical engines with a similar pressure ratio can achieve. The benefit of an intercooler is that it takes less energy to compress cold air that it does for hot air, but air will heat up when compressed. So an intercooler allows a compressor to use less power for a given pressure ratio. Intercoolers are big and heavy and therefore are usually limited to industrial/marine applications. But intercoolers for bypass engines have been developed. These exchange heat between the cold bypass air and the hotter compressed air coming out of the LPC. I don’t think these were adopted to any production engine yet, but it is an area of development.
The fuel cooled oil cooler is a counter current heat exchanger and there are two of them on each J79. Most engines have at least one, and some also have an air cooled oil cooler. If you mean a charge air cooler, then I only know of one engine so equipped, and that is the GE LMS100. It's a huge device, because of the enormous airflow it handles, and it cools the air between the LP compressor and the HP. The GE illustrations show why it could never work in an aircraft. The intercooler is more than twice the size of the whole engine.
You mentioned in the video that there was almost never a problem with the fuel. I can think of the incident where the mechanics mixed the anti-bacterial mixture into the fuel in the wrong ratio and it clogged the fuel regulator. Mentor Pilot has a video about it ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-E4Qclymu2EA.html
@@johnnunn8688 But it seems that, except for water in the fuel, which is usually not a problem in small quantities. The creator of the video is not aware of this. Therefore, it is not a bad idea to talk about it within the community of people who work on airplanes. Besides, the fact that it almost never happens does not mean that it may not happen, as long as the human factor has an influence. I would expect more ideas and examples from someone who works in aviation. Your comment sounds like someone from the PR department.
Well, in the case o DJT, if it was his private aircraft it might be reasonable to have an expedited overhaul of the engines during a period when he didn't expect to use his aircraft.
I saw that program (Mighty Planes? On Discovery?) the issue was the engine's nacelle's not the engines. The nacelles were original to the aircraft as an airframe part, and had the aircraft serial numbers on them. The nacelles were sent out for refinishing/repair, and the contractors just sent off-the-shelf ones back. It was DJT's manager that brought the issue up; I would have done the same. Imagine your original Harley engine was replaced with something unknown.
Uh, it's not a Harley. Industry standards make the quick turnarounds possible. Even though the parts were not engines (thanks for the info), the interchangeable parts seems to work for every airline. Just saying. If it was any other owner, there would be far less tolerance for making such a big stink over an issue that actually does not exist.
Yess, The Pilot Is Driver The Plane , His Not Much Know About The Jet Engine How Is Work, Don't Blame The Pilot His Enocence Person , - Thanks All, - ..... Cheerio .*****.
I suspect that you are making an oblique reference to the use of a forklift to change an engine out on an American Airlines DC-10, which crashed at Chicago O'Hare in 1979. The damage caused to the mounting of the No.1 engine by the improper use of the forklift resulted in the engine detaching on take-off. I suggest we should remember that 271 lives were lost in the crash, plus two fatalities on the ground.
I was going to mention the same thing. Another maintenance shortcut causing a problem. I am particularly bothered by inappropriate maintenance practices.
@@AgentJayZ Using that forklift wasn't just inappropriate, it was totally reprehensible and, in some jurisdictions, might have resulted in criminal charges bering laid.
@AgentJayZ scary to know that after grounding all DC-10 in the US for to AA flight 191 was that the same mechanical malpractice was found in 8 other aircraft.
You may have a video, but since engines are most efficient at full power and planes don't cruise at full power, why don't we see 3-4 engine planes and shut down 1-2 engines at cruise to save fuel?
As discussed in previous videos on my channel... and at length in introductory text books, which maybe you could find... A non-running engine on an airliner wing is a massive source of drag, and several tons of weight. It is expensive, and is subject to wear while windmilling. The oil pumps are driven by the HP system, and won't be turning much, while the LP system will really need oil while freewheeling. These engines cost 20 or so million, and are not designed to freewheel at 500 mph, so warranty does not cover that. Of course, sir you are free to do as you please with the hardware you own. Save a few hundred grand in fuel, but rack up ten times that much in maintenance and inspections. Risk damage to the fragile rep of the airline, and multi millions if bearings get damaged. "Oh, we fixed it"... you gonna fly them? Or another airline that follows standard practice? Ask yourself that...
The USN P-3 Orion patrol aircraft, with Allison turboprops would routinely feather the props of two engines that were shutdown while conducting various searches and/or "loitering" on station in an assigned area. Obviously not at cruising speed.
@@jacquesblaque7728 Thrust stems from accelerating a mass of air. Turboprops do this by turning a propeller, and turbojets do this by accelerating it through internal (ducted) fans (turbine) and exhaust. Unpowered by the Brayton cycle heart of each, both propellers and ducted fans create enormous drag in airflow. Stopping the propellor is a simple task, stopping a ducted fan not so much without severely affecting normal operation. 🤠
@@keepitsimpleengineer I'm more than vaguely aware of the hows, the close parallel between props and turbofans, and the advantage of props to basically be "removed" by feathering. Please note that modern props are not just drag planes but aerodynamic surfaces.
Speaking of fuel, would you know if aviation fuel (av gas) 😮has any issues of algae forming in the tanks. A lot of truckers complain constantly about algae forming and building up in their tanks and fuel system coming from bio grade fuel mixtures. Does av gas do the same?
Avgas is not jet fuel. It's 100 octane gasoline, containing lead, but no ethanol. Recently unleaded Avgas has become approved. Jet Fuel is a mixture of kerosene and other hydrocarbons, and is more similar to diesel than gasoline. There are products to prevent algae buildup in jet fuel, so it must be a bit of a problem. I never deal with aircraft and their fuel systems.
@@AgentJayZ Have you ever read the "Ignition!" book by John Drury Clark? There is a chapter where he describes early efforts to use JP4 as a rocket fuel (in the 1950s if memory serves), and why the enormous difficulties getting this to work resulted in the specifications for RP1, aka rocket grade kerosene. The primary issue with using JP4 and similar fuels in rockets is the olefin (alkene), cycloalkane and aromatic hydrocarbon impurities. These are not a problem for gas turbine engines since they only have to burn the fuel - and usually with a large surplus of air, so combustion tends to be complete, more or less. But most rockets have regenerative cooling passages surrounding the combustion chamber and nozzles, which the fuel is pumped through before it is burned. The extreme heat causes the impurities described above to polymerise and/or form coke deposits, which block up the cooling passages - and if this happens the engine can overheat and undergo catastrophic self-disassembly. Plus the turbopumps on some rockets are often powered by a gas generator running very fuel-rich, so the same polymerisation and coking problems can happen there too, with similarly destructive results. Hence the development of RP1, which is a much more highly refined kerosene with none of the impurities of jet fuels. Anyway, he describes how when the drums of JP4 were delivered, no two samples were ever alike - different boiling ranges, different densities, extremely random composition, even different smells. Plus the discovery that after a drum had been opened and exposed to the air, the JP4 would actually grow bacterial colonies, which generated all sorts of sludges and gunges with disgusting properties and even more cryptic composition. So I'm not surprised in the slightest that jet fuel needs additives to prevent this happening.
@@xcalibertrekker6693 There was an incident where a maintenance tech put WAY too much anti mildew fuel additive in the tanks without pre mixing. All engines shut down.
@@xcalibertrekker6693 Way too early to call that if there is no final report yet. And Sully had no problem with the fuel, on this flight, the air was contaminated... with too much geese.
