Turbojet Horsepower vs Thrust Rating 

"Please go to the cat videos, thank you" I just spit coffee ALL over my computer screen. BUWAHAHAHAHA

Back in the 1960s, when I began my career lifetime in the design of gas turbine engines, industrial, marine and aero, the Industrial Olympus was just entering service at a rating of 17.5MW. It was derived from the Olympus 200 series engine in the Avro Vulcan bomber, which had a take-off rating of 17,000lb thrust. However, the 17.5MW rating was effectively a derating from the aero T/O rating: the industrial gas generator would not have lasted very long at the aero engine's T/O rating - nor would the aero engine. The same basic gas generator, with an improved combustion system based on that of the engine for the Concorde prototypes, plus a cooled HP turbine, designed in the early 1970s, was rated at 30MW. This is the Industrial Olympus that AgentJayZ has shown us in the past.

Keep in mind that both power turbines and electrical generators have an efficiency factor, so measuring the electrical power is less than what the gas turbine is actually making.

Great to see you again! I love listening and learning from your experiences. Hope you have a great Holiday Season!

Thanks for the video, Mister Agent - and I hope you have a great holiday season.

"please go to the cat videos" ROFL That was awesome!

the wealth of knowledge you have provided over the years is astounding,, thank you

Always enjoy the videos. Thank you

Oooooooh! Greg's airplane and Angent Jayz, thurst vs Hp! This is the most interesting internet discussion ever.. Always a pleasure to listen to both of you guys! Merry Christmas and Happy New year!

JayZ. Good to see you back. Hoping all is well up north and that your holidays and upcoming year are the best ever. Thanks for the interesting, no, fascinating content. Keep up the good work.

I’m glad you explained the different fuels and how they compensate between them. I had wondered what they did and if the power changed with different fuels. Makes sense that they’d be able to end up being able to just adjust the fuel flow to get to the desired temps. I’m so used to piston engines it’s sometimes difficult to wrap my head around the turbine engines.

Excellent video , Happy holidays and Merry Christmas AgentJayZ !

Thank you for doing these videos

AJZ Happy Holidays thanks for an informative and entertaining video. Having worked on J79 (LM1500) in a USN Patrol Gunboat BITD which was rated at 12,900 SHP and drove the 240T 165' boat to 45-50knts. Also after Navy I worked at Lockheed ADP who built the F104 which also had a single J79 W AB and did Mach2.2+. I also worked at a So Cal Utiltiy for 31 yrs where We had 8 PW GG4s (J75s) exhausting on expander turbines that created 180MW of emergency peaker electrical power in about 2min from turning gear to 3550 srpm where field brkrs closed and at 3600 srpm w system synchronized. Stay Healthy.

Missed you! Merry Christmas!

Fantastic! Thank you for your in depth explanation!

The only thing you said that I understood was "go to the cat videos" but after 25 minutes I was still watching this. Jokes aside, this was a great explanation to a question that on the surface seems very simple, but in reality is like trying to compare oranges to lemons.

You nail this. It is all about the frame of reference as soon as people try and do apples and apples comparisons but then fail to treat it as an energy in versus energy out black box model. And the comparisons between a turbojet and a piston engine measuring horsepower at the fly wheel? C’mon!! Madness.

Hey, I love cat videos. But I like your videos even more. I've learned a lot from you.

merry christmas jay :) hope you're safe!

Addicting content.

got the math at the end a bit tounge tangled i think; one megawatt is 1000 killo watts, or 1 million watts (1000 killowats), making it 1 kilowatt of power roughly equals one pound of thrust, or 1.3 ish horsepower per pound

Merry Christmas sir. Hope you have a fantastic New Year

Bit late to the party, but really great to see your take on it, talking about the actual usable power that the engine can make. This contrasts nicely with Greg's video on the Tomcat's horsepower, at a very different take, looking at propulsive power usable for overcoming aircraft drag and accelerating it (which is effected by its thrust directly). As you said in the beginning, no equation, and tons of equations, depending on your point of view. Thanks.

As it’s Christmas, can I recite my party piece, please? If you have an aircraft in horizontal flight at constant speed and you know (or can calculate) the thrust of the engines at that flight condition - or you know (or can calculate) the drag force on the aircraft, then you can work out the actual horsepower that the engines are effectively delivering. You know the velocity of the aircraft (in ft/sec). You know the force that the engines are working against (in lb force) - and thrust equals drag, of course. You can multiply one by the other and divide by James Watt’s magic number of 550 - and, hey presto, that is the horsepower figure for the engines at that condition. Do that for Concorde in supersonic cruise at 1,350 miles /hr, at an altitude of 58,000ft, where the four Olympus 593 engines were producing 9,000lb thrust each. The answer? Near enough 130,000 horsepower. And a Merry Christmas everyone!

Hello from Ukraine. Happy New Year. Thanks for your channel. I always look with pleasure. I wish you good health.

A new JayZ video in time for Christmas - thank you Santa!

Our current project at work is a little number we call the _GE9X._ The horsepower that we pull out to use to power accessories alone is quite amazing.

May You Have A Merry Christmas And A Happy and Healthy New Year

I was driving with a mate back when I was young, and a semi was 2 metres from the back of our car when a front tyre blew out. Oh man I thought I'd not get a chance to grow old. No turn offs available so I helped the driver steady the steering at 75MPH. Then we ended up on a hill and the wheel nuts were rattle gunned on. Had to find a large boulder to mount the L shape tool onto, while getting the driver to drive forward gingerly. Took a while.

Top! Um Mestre!

Merry Christmas and a Happy New Year to all!

It is funny why it is so important to concert thrust to horse power or kW. My light bulbs makes Candela / Lumen, why don't we convert this to Watts too. Thanks for all your great videos, I have learned a lot from them

Greg did a good video on the horsepower of the F-14

JZ, I’ve been thinking when an engine is fixed to the ground and running it is moving and doing work. Not only is it moving the air as you explain, it’s also changing the rotation of the planet. It’s just hard to measure 🤣

Just multiply the thrust in Newtons by the exhaust velocity in m/s to get the power rating in W.

I like that answer, "It depends,... or who cares?!" I'm good with that.

Slightly off the topic of this vid, but sort of relevant. I've watch pretty much all your vids, and haven't seen one that explains how the thrust produced at the accelerating nozzle is mechanically transmitted to the airframe/mounts. Love the depth of detail you go into.

G'day Jay, Yay Team ! I was wondering where you'd got to, good to see you back in my feed. I'm olde Skool mate, my idea of a HorseyPower is the 50-pound Wooden Bucket with 10 Imperial Gallons of Water weighing 550 Pounds gross between them, with a 1-inch diameter Rope (officially weightless according to the allegation !) leading straight up the Mineshaft and over a 1-ft diameter Pulley, harnessed to a Horse...; the Horse walks away at 1 Foot per Second (0.68 mph), and thus the 550 Pounds is lifted vertically at 1 Foot per Second. Last time I actually used the equation was "test flying" my eBike on the neighbour's Driveway, with me and the Bike with 2 spare Batteries (220 pounds) travelling 1 Km in 3 minutes and climbing 40 metres (126 ft) at an indicated average groundspeed of 19 Km/Hr. I make it out that the Vertical Lifting equates to the Hub-Motor delivering 0.16 Horsepower to lift the weight up that height in that time...; and I pluck from my Arse the guess that the work overcoming Aerodynamic Drag plus the work overcoming Rolling Resistance (bouncing over the rocky Dirt Driveway) is about equal to the work of lifting the Weight in the time. All done without my input to the Pedals, so the "250 Watt Motor" does 0.32 Horsepower worth of work, and with a Horsepower being "half a Columbus (1492/2= 746 Watts !), then a third of 746 equals 248.6 Watts of Twistiness and 1.4 Watts wasted as Heat...(the Motor warms up from 28 degrees C. to 31 during the 3 minutes !) So, them there Chinamen sure seem to know what they're doing, when it comes to making Electric Bicycles, and the Maths more or less works out. Comparing Horses to Watts to Twistiness in a Shaft to Air Displacement and Wind to Thrust is always goanna be an approximation founded in Guesswork, but it feels good when the numbers indicate that our Guesses are "somewhere close to reality" ; I guess (!). Anyway mate, to collect your reward (having a few giggles about Biggles !), please feel free to backtrack me to my Videos, therein to find, "The Aviator's Moustache..., Mystery Solved !" Its only 56 seconds duration, but it relies on a New Scientist magazine Photo Feature, so it might be not-wrong (?) ! Happy Solstice Festival ! Such is life, Have a good one... Stay safe. ;-p Ciao !

Four Lm2500 engines power the Spruance DD-963 class destroyers. Thanks to point out that this engine is an power turbine version of the Cf-6 aeroengine.

Did search for but only found half cutaway J79 had a really good search, wanted to make a laminated one for my wall

There are two engine options on the Boeing 787. A General Electric GEnx or a Rolls Royce Trent 1000

Well, as Jay said, it comes down to mass-flow. Measuring that on the exhaust of these things is difficult. And, the measurement method will to some extent affect the performance of the engine. For aircraft, knowing the thrust is enough, because the drag of the aircraft can be calculated. For a power turbine, to get some idea of shaft horsepower output, you need to have some idea of mass-flow out of the gas generator...

loved the " go watch cat videos" comment.... cracked me up.

consider the efficiency of the pt, a jet generator can put out 10x energy per sec but the pt output may have 5x at the 50% efficient pt+electric generator combo

BK below has it. If thrust and gas velocity can be measured no PT or other device reqd. SI units to get P in Watts.

I've always used a very rough rule-of-thumb as 2.5 lbs of thrust makes 1 hp. I used to fly a Citation C-550 which had 5,000 lbs thrust in total and it felt like it had about 2,000 hp. When I was flying 747's I once stuck a car accelerometer on it for one take-off and it came up with 72,000 hp, which was about 2.5:1 with the thrust.

For a turbofan....how much shaft horsepower would it take to turn the fan at takeoff rated thrust? It's a lot. When talking to people I always give it 1:1 ratio. 60,000lbs of thrust takes roughly 60,000 horsepower to turn the fan at that RPM. Rough estimate, but it's ballpark.

I did some rough thrust calculation based on a piston engine at x HP at x rpm with x axle ratio and x tire diameter. This gets thrust at the tires and also a headache

I am pretty sure, one can convert thrust to power... BUT: The way you measure power and thrust has to be the same on all tests you do to get the calibration curve. Also the effeciancy of the Thrust-to-Power-Converter (aka the powerturbine/backpressuregenerator/whatever-else-you-are-using) has to be the same on all tests. To conclude: the Conversionfactor of Thrust-to-Power is dependent on the conversion device in use

23:50 RR TRENT 1000 GE NX But I am sure you know this by now but there is group belief phenomenon where they think it already done like 999 or 911

If you really want to break someone's brain, we can show that 180 horsepower equals both 600 lbs of thrust and 1,370 lbs of thrust. My 1964 M20C, powered by a 180 HP Lycoming O-360, has a 500 ft takeoff roll at 2200 lbs gross weight, at sea level on a cold day. This maths out to about 600 lbf thrust. The Robinson R-22 helicopter idea a nearly identical 180 HP Lycoming HO-360, H being the "helicopter" designation. The R-22 has a Max grid weight of 1,370 lbs, and it can hover at that weight. So, 180 hp produces either 600 or 1,400 lbf thrust, depending on what spinny things you connect it to.

How many HP will the Orenda Iroquois make when you have it running?

Stereo amplifiers are rated in watts. By how much power they deliver to the speakers, which rattle air to make sound. At jet exhaust, the power of the air being accelerated also is 'wasted' to make sound. That can be measured in decibels. As loud as jets are, the sound wattage is only a tiny fraction of the acceleration wattage. Accelerated air + vibrating air = power out. Little side note.

is this a reaction to Greg's Airplanes and Automobiles or just a coincidence that you made video on this topic?

I’m fine with the “A metric mega-shit-ton” as an answer for turbo jet thrust to horsepower conversion. Just change the HP to KW to keep things simple, even for us Americans.

Why do I watch, because I use to repair gas turbines and screw turbines, I balanced them plus ultrasound the turbine blades. But now retired and want to see if anything has changed in the industry. But it's all the same.

North American A-5 Vigilante. J-79 engines.

Horsepower and thrust are a way of measuring propulsive force. 1000 pounds of thrust coming from a taxiing jumbo jet engine will be created with a rear nozzle velocity of...300mph. 1000 pounds of thrust coming from a small jet trainer engine at takeoff has a rear nozzle velocity of mach 3 or more. A 500 horsepower piston engine propeller driven stunt plane might produce 3000 pounds of thrust at takeoff and while performing. Take that same engine and put it in a aerodynamically sleak go fast plane and it might reach airspeeds of 400mph+. The 1000lb thrust jet trainer will go 100-200mph faster. Equating thrust to horsepower has more in common with trying to compare apples to oranges7

Efficiency seems to be a big variable . IC engines seem to be rated in terms of BSFC, lbs per hour per HP. The figure is usually between .4 and .5. There must be some equivalent for a turbine engine?

W=T*V, V for speed so you can only has full power in ISO and sea lever; the idea of think a airplane engine and industry gas turbo was okay but if you has different fuel control it may off set.

Merry Christmas, LM2500 could be a nice example. As you know the big guy generates 30000-33000 sHP and 25 MW. When you tested it, you used a exhaust nozzle so you convert the gas generator to jet engine easily. when the Lm2500’s Gas generator testing (with exhaust nozzle, no power turbine), we can obtain the thrust. There is no problem but how we can get the Horsepower (ex: 8000 rpm or 9000 rpm) ? Thanks

Horsepower is defined as the amount of work over time. That to me seems very vague. How do you measure work? What is work? In a car it's could be how much it is pushing to car to overcome weight and friction. How can that be measured in a jet? Or driving a generator? You are right, it can be confusing. Going to watch cat videos now...

Yo big jay. How many different fuels will your turbines run on? Not the black bird or new equipment. Just what you work on. I’m able to use kerosene, jet1A,or diesel fuel in the small jetcat engines. Just was wondering.

Hey, I’m having a question that wasn’t talked about just yet, if I’m not mistaking. It’s especially regarding older Turboshaft engines, with a one shaft design (take the Alouette II with it’s Artouste engine as an example). Being a one shaft turboshaft must mean they’re unable to start under load just as a piston engine would because spinning the compressor in first place would mean the starter would have to spin the whole Rotor and gearbox assembly, right? So do they have manually engageable clutches like cars? Or does the term „One shaft“ just ignore the shaft and the stage of the working turbine? I‘m currently an apprentice and my Instructor couldn’t tell me! Thank you very much in advance and marry Christmas! Greetings Louis

regarding the discussion about the equivalent power to thrust ratio, and how the book mentions 2:1 I'm assuming that even when operating the engine with an output shaft, it still produces "some" thrust with the exhaust gasses? So maybe this thrust could equate to some equivalent power that cannot be converted to mechanical work at the output shaft. Could the book be taking that into account to measure the equivalence? As in, it produces X ammount of power but only Y% of that thrust can be harvested at the output shaft? And the other (100-Y)% is still converted to work in accelerating air mass? If that makes sense.

It's hard to solve an equation with missing variables that substantially change the result. It's people trying to understand with something relatable asking "how much hp that thang got"... I'm going to start purchasing lightbulbs in horsepower from now on. No more 60watt bulbs. You guys have those .08hp bulbs? haha....

HP is about the same as kinetic energy of exhaust gas per second at engine exhaust nozzle? Another question, why the by pass route of big turbo fan engine is not streamlined (pipes etc disturbing the flow)?

safe to say a pile of power however you measure

It only does seem counter-intuitive that there is no "clear" factor for conversion, because the fact that planes fly faster/higher with more thrust seems to be comparable to fly faster and higher with more horsepower. But it does not really make sense, because both ratings are actually outputs for different uses on different systems. Kinda like with cars where horsepower and torque are linked - but also not. There are tractors with 60 PS that plow through a field as if it was warm butter, but if you try to pull the plow with your 600 PS Supersportscar it won't move a single meter. So what matters is pulling force or speed but both setups are influenced by gearbox, fuel, rpm etc. Most importantly, max torqe and max speed are not at the same rpm. Similar for Thrust and Horsepower on the Jet engine. The engine is setup to produce max thrust at the mounting point for an airplain, so it can fly efficient. But in a powerplant it is setup for using the least fuel to produce a certain power output. So for flying you want to move a maximum ammount of air at highest possible speed, therefore you accept to make a compromise on how much fuel you burn. If needed you just add extra tanks. In powerplants you have a certain ammount of fuel and you dont need thrust. So you want to extract as much energy from the airflow and put it in the generator. So you want enough air to burn you fuel completely and than get that energy the moving air transports as completly as possible from your turbine. So thrust or horsepower are different sides of the same medal: Energy. You have a fuel that stores a certain ammount of caloric energy that gets set free in the combustion. That energy causes the rise of pressure and temperature in the gas inside the engine, so it can be transormed into mechanical work. You can now try to move as much air as possible and create a high ammount of thrust with that energy, therefore you put a turbine in the gas that has low stage count and doesn't hinder the airflow to much so it doesn't lose speed, you just want the system to be self sustaining and increase fuel input to get faster and faster by hotter and hotter air. On the other hand if you have fix ammount of fuel (it is what ou pay for as powerplant) to fulfill a need of power, you try to get as much energy out of the exaust gas with the turbine, so you don't open bypasses, you slow the gas down in the turbine as much as possible to gain mximum torqe for the input to the generator and you just leave enough torque on the engine shaft to feed itself with enoug air for a clean combustion of the fuel. That also means you dont get thrust ideally, because the mechanical work shall be put to the generator and not into accelaration of air in the exhaust. So yes, from the physics side you can calculate the ammount of thrust to the ammount of calorimetric enrgy you put in the engine. And you can also calculate an ammount of horsepower for that fuel consumption. So there is a factor between horsepower and thrust and trust and horespower will scale for that engine to that factor if the ammount of oxygen in the air the engine consumes changes for example. But that factor is dependent on the engine tuning in its use-case and cannot be just copied for another engine. Of course that does not answer the question completely, because you cpuld now make a deepdive how to define "horsepower" of an engine by asking if you talk about mechanical work on compressor/fasn blades or turbine output work or whatever you want to take energy from to measure it...

I realize I'm being pedantic here but are the fuel atomizers different between ones that accept aircraft grade kerosene and natural gas / propane? It seems with the LM1500s your shown tested, some of the plumbing looks a bit different.

My simplistic understanding is this ..... Automobile engines are not typically described in terms of thrust or units of force because they do not produce a direct force to propel the vehicle forward in the same way that a jet engine does. In an automobile engine, the power output is used to turn the wheels of the vehicle through a transmission and other mechanical components. The force that is produced by the engine is transmitted through the drive-train to the wheels, which then apply the force to the ground to move the vehicle forward. Therefore, while force is involved in the operation of an automobile engine, it is not the primary output of the engine, and it is not a direct measure of the engine's ability to propel the vehicle forward. In contrast, thrust is the primary output of a jet engine and is a direct measure of the engine's ability to propel an aircraft forward through the air. Therefore, thrust is a more useful measure for jet engines, while horsepower is a more useful measure for automobile engines, because it provides a direct measure of the engine's ability to turn the wheels and move the vehicle forward.

got a question, tried to find it mentioned before but can not find it so here we go : If you got a gearbox connected to the N1-shaft and it brakes and stops the N1 fan completely .. is it likely that the N2 continues to run .. ( although with somewhat disturbed airflow from the front ?

The engine should have a thermodynamic power rating. There is some amount of available power from the fuel burnt. But that's theoretical, not practical useful output power. For example they say that PT-6 has thermodynamically (gas generator) around 300hp more than on the output shaft. Don't quote me on the numbers, but principal should be clear.

At what point internally does the engine go from huff to puff? At the combustion chamber? GE made...made good lightbulbs.

If you used ethanol instead of kerosene in a gas turbine, would the fuel control manage to inject twice the volume of fuel? Does it have that kind of overcapacity built in without having to modify anything?

Actually even more "confusing": if you have the same gas generator with the same fuel and air flow (so it is fair to assume the same horse power) and then build a tubojet and a turbofan with it, the thrust will be very different! I don't know if some manufacturer has ever done this transformation (from turbojet to turbofan or turboprop) but it's a comon theoretical exercise.

It's striking how long turbines have been limited mostly by materials science alone - the temperatures at which things melt or lose strength. The mechanical engineering is so optimized. It's said the Pratt & Whitney F135 approaches 2,000°C (when all the coatings are in good condition). Is that going to be the end unless new materials are discovered?

Would it make any sense to use radioactive isotopes of air molecules to directly observe turbulences inside the engine and use that data to find out a way to reduce Reynolds number right to zero ? And had you ever heard about exoskeletal turbojet engines ?

Question it would be cool to hear you answer: what is the effect of heavy rain on a turbojet or turbofan in flight? I heard somewhere it improves performance due to the increased mass transfer. But it must at some point become a detriment and eventually stop the engine.

haven't watched one of your video for a while got AJZ withdrawal I think, missed your jet education

how did u learn so much about jhet engines and made one homemade so fast how long did it take ya? will a thermodynamics course help a lot? i only took 1 thermodybnamic course in my life and it was about those adiabatic stuff and control volume control mass and enclosed work-energy area from the specific volumes stuff i forgot but im sure theres more. u keep talking about newtonian mechanics on the particle level, so will classical mechanics help a lot and did ya learn that? what if i wanna learn about rc engines and building just small jet engines i can put on a go kart where do i start??? then what if i wanna move on next to big engines what should i do? ya seem like a smart dude its like u know every nerve and fiber of that big saber engine video, u stripped it down and tested it without exploding into failure and basically knew every part of it and a bit of everything in all engineering departments needed to inspect that engine before safely running it as is likely the standard in the jet engine companies of the real world.

Interesting. However the same engine that produces 7000 pounds of thrust when stationary will produce more when in high speed flight.

Wow. So both engines actually produced a ratio of 1. (1lbt was roughly equivalent to 1kW) 7280 lbt engine produced 7MW or 7000 kW. 11500 lbt engine produced 15000hp which is 11194 kW.

My humble thoughts... Horsepower is a unit of power. Pounds of thrust is a unit of force. You simply can't convert those units. It would be like trying to convert a unit of length to a unit of temperature. Or am I misunderstanding what is meant by "pounds of thrust" in the gas turbine world? Is this similar to the relationship between torque and horsepower in an automotive engine? They both say a lot about what the engine "can do" but they represent two different things. Interestingly enough I ran the conversion calculations for your two examples and got 1.3 hp per lb thrust for both examples... coincidence? (7MW = 7,280 lb thrust. 15,000hp = 11,500lb thrust).

It amazes me that pistons were popular first...

I'm curious: do you guys have any access to a J79-GE-J1E, or are those more rare these days?

What ever happened to the Turbo Jet Boat?

I think your math is wrong brother, 15,000 hp is 11.19 Megawatt, so follows the same rough 1:1 relationship between MW and Thrust. Great vid, nice to think through this stuff. I always thought Turbines had direct relationship to HP, turning shaft has torque and RPM....may be tough to measure, but theoretically it's calculatable and measurable. I'd guess the newer engines do a much better job of turning rotational power into thrust (efficiency), so thrust measurements to hp correlation is likely very different between eras..

Off topic: Does anyone have extensive experience with the engine used in the U.S. B57? I was in the Cal ANG when we had a B57 come by TDY for a few weeks. I swear, every post flight, I poured in 3-4 quarts of lube oil. What was annoying was that the filler was in a gawdawful position and it always looked full. I was told to keep pouring until it overflowed. Comments please?

GE and ABB gas turbines

I know most electrica RC plane motor with propeller give about 4 gram per watt. which is 2 times more efficient

Watts = PIE. Power = Amps x Volts

De Laval nozzle...

Jay, Merry Christmas and thanks for another year of turbine nerd content. I saw this photo of an French aerotrain with a wild exhaust nozzle; can you tell me why it's shaped like this? It looks jet-ish in the front and a lot like my propane grill in the back. ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-ND3MegqYQFA.html

787 uses a RR Trent

@AgentJayZ, John from Australia here. I see it like this, in a thrust rated engine it takes X Horsepower to create X thrust. My reasoning is this: to spin the compressor at full thrust it takes HP, lots of HP. With a big fan on the front, you'd have to add to power turbine output. In an engine rated for shaft HP, it's rather obvious. Unless there is a shaft output creating rotating torque, you'd have to use Horse-Farts as there is no torque. No rotating torque, NO POWER! You could just convert the BTU output to HP, but not really useful.

HP is work done over time You can produce infinite amounts of thrust but if no movement no work is done that’s why to convert thrust to HP it needs to be at speed and see level

Most of the parts in a J-79 are steel. This it could have been lighter with the exotic metals.

I thought trust acts on the pressure made by the compressor was I even A bit close ?