How is JZee's brain output affected at extremes ends of his operating temp limits...? let's graph it.

In the C-130 turbo-prop world, we're able to determine engine power by measuring the twist between a pair of concentric shafts that connect the prop's reduction gear box to the power stages of the turbine. The inner shaft transmits the engine's torque while the outer shaft free floats at one end. At the free floated end, there's a set of teeth on each shaft. When the engine is off these teeth are aligned. When torque is applied by the motor, the inner shaft twists and we're able to measure the offset between the two shafts with hall effect sensors. The higher the torque, the higher the offset between the teeth. Then a gauge in the flight deck measures the offset of the teeth and gives you engine torque indication. On the old T56 motors we didn't even track EPR at the flightline maintenance level. It was only used occasionally at depot or test cell. Now the new AE2100D3's log it behind the scenes and we use it for long term engine health monitoring.

A joint live chat with Blancolirio would be interesting wherein he could possibly discuss how pilots are trained to use EPR in their work.

@AgentJayZ thank you for the referral and positive endorsement. It was a very pleasent surprise to hear you mention me as I have watched many of your videos. Your comments about the increase in stagnation pressure at the compessor inlet when the aircraft speeds up are correct. I didn't mention this as I wanted to give a brief overview, but you were right to point it out. As regards the pronounciation of "t" and "th", you are also correct, but where I grew up in Ireland these pronounciations are particularly accented, and it was enjoyable to hear your description of it. You can be assured that I will be playing it to my friends in the pub some night. Please keep up the great work that you do

My simple run with EPR is that as the machine became more self managed, the lovely human factors engineers got rid of a lot of engine data that we have no control over because it is no longer relevant to the pilot and somewhat simplified it down to some basic numbers of "performance health". EPR it's also more prominent in some manufacturers design systems over others. Performance changes with all sorts of atmospheric conditions so the EPR is a fairly handy way to see how the engine is performing for given conditions. It's also really easy to ignore which is great because most guys do.

Gee, you make it sound like my 20 years in the Air Force repairing EPR systems on B-52s and KC-135s was a waste of time. Thanks. It would have been so much easier just to tell the pilots, "Aw, you don't need EPR."

You are right, in most cases the airspeed indicator is the much more important instrument. One main reason why a pilot needs some indication of thrust is when the airspeed indication fails (or is suspected to be unreliable). In that case, the manual has tables on what thrust and what pitch angle to set, depending on gross weight, so the aircraft will continue to fly stable. Rough values are often memory items, and a finer setup can then be found in the manual.

When I was a crew chief on B-52 H models (powered by Pratt &Whitney TF-33 low bypass turbofans)in the 1980s we had a probe right in front of the IGVs called a PT2 probe and another probe in the turbine section called the PT7 probe. These were connected by lines to the transducer which was under an engine strut fairing behind the engines which was called a sailboat. If we had an EPR write up we had to drop the sailboat and connect lines going to the transducer to a ground test unit and then pump a predetermined amount of air pressure into the lines coming off both probes and see what the test unit was showing as the EPR was reading for the simulated pressure we were were pumping into the probed. 99% of the time the problem was a bad transducer which was subject to alot if vibration at the location Boeing elected to install it. The 1% of failures was became line for the PT2 probe was leaking at the connection where the ring cowl attaches to the front of the fan case as the PT2 probe was physically mounted to the ring cowl Nice video and good explanation of what this reading is and why it is useful to the flight crew. Another interesting thing of note, I also crewed on B-52 G models that pure jets without fans. To get additional thrust for a heavy takeoff we used water injection. The EPR gages really came alive when the water was turned on and consequently dropped off considerably when we ran out of water 90 seconds later

A little tidbit about modern engines: The A350 uses a cockpit indication of "% thrust", which the manual says is calculated from engine parameters, but not actually measured. It says 100% is "thrust with levers at TOGA and bleed off", so it is always relative to the maximum available, depending on altitude and temperature.

Back around 1980, I was in the Marines working on A-4 and TA-4 Skyhawks avionics. There was an EPR transducer and indicator for the P&W J52 engine. I had the pleasure of a few rides in the back seat of the TA-4's, but one was aborted midway through the take-off because the EPR indication was off. For the Skyhawk, the EPR reading seemed to be an indication of a properly functioning engine, especially during the critical take-off period. Thanks for the video and explanation!

Don't think you are a jerk. Not by a long stretch. Do you have to spoon feed non-engineers? We really appreciate the time you take to 'non-laymanize' the jet turbine - a fascinating piece of equipment to many... The more videos of yours I watch, the more interested I am. One question though, are you an engineer or did you attend SAIT or NAIT like me?

For what it's worth I fly a 767, some with GE engines, some with P&W. The Pratt's have EPR displayed above N1 on the EICAS, but it's completely disregarded. Gives us no useful information....to the point that it's not even available on the GEs. N1 is the reference off of which all our performance is calculated and derived. Just how my airline flys our 767s with our engines. Your mileage may vary.

I have flown 727's with P&W JT8D's around the world, 747's with JT9's around the world, 747's with GE CF6's around the world, 757's with Rolls Royce RB-211's around the country, and now I fly 767's with GE CF6-80 engines. Now a-days, I just let the autothrottles set the power. But frankly? RPM always made more sense to me, the way that GE does it, since these don't use EPR. Remember now, EPR is what caused the Air Florida crash in Washington DC. But anyway, I can drive a car in KM/h or mph, it doesn't make any difference at all. But I will say that GE engines give a hell of a lot less trouble than P&W engines. They start quicker. RR stuff? Never had a problem with them, so they are basically GE's with an EPR gauge.

@12:51 "Okay. We've seen this one before. It's from 1972, so you know it's right up to date." Amusing.

Jzee I would like to comment to simplify things for your audience. EPR is used by the engine/aircraft manufacturers as a precise way of allowing pilots to set throttles(power settings) during certain phases of flt .Pratt and RR tend to think it's more precise than GE although GE also uses EPR as backup ind should N1 ind fail and conversely for RR and Pratt.When the AME 's Do ground runups to check the health on all those types of engines mentioned we use tuning charts for the temp and field baro press of the day to find the target for certain throttle setting .For example part power for a Dc9 Jt8d engine is 1.65 epr .Take off. a little over 2.0 .A L1011 -200 with RB211 engines with all bleeds active would be around 1.516 epr .The lower reading reflects the different eng locations than the pratt from which EPR is chosen from..But if the targets are met and all other parameters such as n1, n2 ,n3, egt,fuel flow etc are met the engine is healthy.

Awesome explanation. 100% correct on pilot being 50+ feet away from the engines. On my plane they're easily 120'+ feet from 2 of them and 160' from the 3rd. As operators, power plus attitude = performance. When flying J52s in military I could set a specific fuel flow and get the desired airspeed and performance I wanted. On my turboprop, setting 26 ft-lbs when fully configured will hold 120 kts + 500fpm every time. (Set it and forget it - so to speak) Absolutely vital when busy doing other tasks. In both cases EGT/EPR and N1/N2 really didn't tell me useful information. Other times it does.

Thank you for all the years of video’s and book recommendations. Got in the field myself because of them. (On LEAP now)

Hi AgentJayZ. At around 18:50, you mentioned my name. My first comment is that the engine station numbers for pressure (and temperature) measurement are not necessarily governed by an international standard. For R-R's station numbers for a "typical" two-spool, low-bypass engine of the 1960s, take a look at page 216 of your copy of 'The Jet Engine'. What the station numbers are for a "typical" three-spool engine, I can't recall: in any case they are bound to be different for a three-spool engine. My second comment has already been made by others: you inverted the numerator and denominator of the EPR.

Load cell. Very useful for measuring thrust production or fat gain.

Good video, great description. Roddy's vid is good, and channel has lots of good concise videos in that lovely accent. Loved the "I'm not a jerk, but I play one on TV."

Very descriptive. Nice to have a breakdown of the semi-standardised usage of Px measurement points also. Thanks!

Regarding the bit of turbocharger history at 4:48, the turbocharger was patented in 1905 by Alfred Buchi as a means to increase the efficiency of diesel engines used in marine propulsion. The aircraft turbocharger did not arrive until after 1918 when a General Electric turbocharger was fitted to a WW1 surplus Liberty engine and tested on Pikes Peak. N1 seems like the better choice for takeoff performance monitoring, it reflects the mass flow through the LP turbine which is directly related to compressor performance and fuel flow.

I think you and your channel are great! Thanks for everything!

Great explanation on the EPR. I have used resistive strain sensors that are glued on the structure on the axis of interest. Really sensitive, even expansion due to minor changes in ambient temperature is readable and has to be taken into account for calibration.

Only some engine OEMs actually use EPR as primary thrust indication. Many actually just use percentage N1 (percentage of the maximum spool RPM). Most modern Rolls Royce engines use EPR while most GE/CFM and PW engines use N1% indications. The CFM 56 and the LEAP-1B (and thus both 737 NG and MAX) use N1 for thrust setting.

Interesting explanation. Makes more sense of why it would be in aircraft but not so much in your industry. Will check out more info.

Ohh man! Peter Vosbury was my engines and propulsion professor at Embry Riddle back in 2007! I still reference that book as the Tech Sales dude for a major Aerospace company.

Great video. You do not "suffer fools gladly". Neither I. But you inform and educate. I really appreciate that. Thank you. One small nit... Evendale Ohio is pronounced with "eee" on the front end. (pronounced EE-vən-dayl). I was born in Hamilton County, that's how we said it there. Potayto, potahto. 🙂

Interesting to see what TLAs (Three Letter Acronyms) mean in other fields. To me EPR is Electron Paramagnetic Resonance, I thought you had bought one to do some kind of analysis. Hope you got that heater working before the continent wide snow storm came.

As always, I really enjoyed the vid, and I learned. Thanks yet again.

Assignment completed. Watched, liked and subscribed.

Thanks for cool videos! Greetings from Stockholm!

Do-hickey....the ultimate tech term. LOL Great vids Jay

I watched you EPR link video, not even going attempt his name it was interesting thank you

@20:45 - as a pilot, I want to know how hard the engine is pushing because i need to stay ahead of the plane. How fast the plane is going tells me how hard the engine was pushing ten seconds ago. When I'm setting up for an approach, i need to know how hard the engine is pushing now, so that i can get to the correct speed and descent rate at the correct point in the sky 2 minutes ahead of me.

Thanks...outstanding explanations. I operated gas turbines at Ram River gas plant for years..Did you ever rebuild any of our jets?I think you may have years ago.

I love your snappy remarks to dumb questions! I just try not to be on the receiving end of them! I only saw EPR gauges on a turbojet 737-200.. all modern turbo fans that I’ve flown (CRJ -700, 900 and 737-300 though 700MAX all use N1 for power settings. I don’t know if other airliners use EPR.. As for the 737-200 that used EPR, we would use that for takeoff power setting, then we would reference N1, EGT, and Fuel Flow in flight.

Hi, can you show us the accessories around the engine? Thank you for filming these videos, very informative!

I can attest to the LEAP engine on the MAX is really fuel efficient, and quiet, but boy are they slow to start.. there’s a Bowed Rotor motoring sequence that takes up to a minute before you can even introduce fuel, then the acceleration is really slow, then the required idle warm up time.. then after landing, there’s a required idle cool down time.. Also the 737 uses the CFM engine not just on the Next Gen versions, but also the classic -300, -400, -500. The NG was a more powerful version of the CFM engine.

Remember when them piezo cells were expensive. The architects built a multi story library at my college in 1977 and did not take into account the weight of the books (Syracuse U) .We put those suckers on all the beams (cut holes in finished walls) and put a big-ass swimming pool on the roof and made waves in it.

The station numbers in your manuals vary by engine design and manufacturer. If you are able to use the thermodynamic Enthalpy-Entropy, Staticpressure-density diagrams, the EPR is easier to understand.

You can’t accurately measure thrust at the engine mount unless the plane itself is in a constant state with no accelerations. The thrust read out would tell you the amount of thrust being produced which will be relative to the drag of the aircraft at that constant state which is potentially useful. Armchair enthusiasts do tend to forget how different installed sea level static thrust sitting on the end of the runway can be from cruise thrust at 35000 feet. I’m not a pilot but I can understand why actual engine metrics are more important than simply the end result of all those read outs, esp when thrust can vary so highly relative to altitude and speed.

Great video thanks

@AgentJayZ Thanks for this great video! I would like to add more for those who seek deeper info further to what you elaborated nicely! EPR basically manifests the engine operating (power setting) status to the pilots to know engines live performance. Apart from this, EPR becomes particularly important when multiple data being transmitted by the EEC (Engine Electronic Controller) doesn't agree with each others. For example in a failure scenario. (Of course alone EPR may not be 100% realible in all kind of catastrophic incidents) Let's say an accident has caused significant damage to the system that transmits the pilot's throttle setting input to the engine fuel supply system. In this case, regardless of lever setting the engine may continue to receive fuel supply; and this pilots can easily detect upon looking at EPR. Please refer to the video of Trent900 in-flight disc failure event that took place for the Australian A380 airliner. Now moving to the topic tht still seems a daunting question for many! The change from EPR to N1. As explained in this video, EPR is a term that consists of various parameters. This is due to the mission requirement of operating in wider range of climat and flight conditions. However, this brings a serious problem. Relying on several measured parameters is, as per experience, not so reliable. When one or more probe fails, it starts generating random numbers. Which eventually results in falsified EPR calculations. (For information, there are no multiple sensors installed on an engine to act as a back up unit. The answer to why we don't have is not so straight forward.) Moreover, there has always been staggering issues with the icing/ice accumulation. Some probes do experience icing at a greater level due to their location on propulsion systems, which affects their nominal functionality. And if required, I will need to create a video to explain the issue with EPR or TPR in maintaining thrust as engine erodes. There could be more issues as well, which I might have not covered! To get rid of these problems, N1 controlled engines appears more realible. This is because of its simplicity - the sensor that is mounted to record shaft rotational speed directly without any conversion. And remember, it is only a single sensor. Not a hack of many !

It's okay buddy. Many of us suffer from being dismissive assholes when we think people are asking us stupid questions. It's what happens when you know too much about something. Couldn't tell you how many times I've had to apologize the next day after dismissing someone for making what sounded like a stupid comment. Fallible humans all of us. I've even asked some stupid questions myself on things I didn't know enough about to ask the right question.

Thank you Sir!!! I have question- Is inlet guide vane eliminates noise in turbo fan??? Why hot& cold gas mixing( in noise suppressors) reduce noise ???

I'm confused a bit. In Roddy's video, he compared the inlet (I) and outlet (O) pressures by dividing P9 by P1, or O/I. On the laminated photocopy, you indicated I/O. Do some gauges show I/O while others show O/I? The ISBN is that number in the square in the center of the back cover that you showed. It's a unique identifier for any book. What you showed was the SKU (stock-keeping unit). You're not a jerk by telling it how it is. The jerks are the ones who argue with you or try to tell you that you're wrong when you're right. And then you prove it with your years of experience and knowledge, plus by showing the source of your information. Keep being a "jerk" if that's what the real jerks wanna call it. You're alright in my book!

Q. the F86 or the Canadair Saber in the background, I see it moving, is it synced to a clock or is it just a random movement ?

Thank you for this! I was so confused by EPR. Not knowing what it was, I made the guess it was the ratio of inlet to compressor outlet. But that made no sense as the number was WAY too low.

At the beginning where he's explaining how they measure engine pressure ratio I think he means load cells. They turn metal deformation into electrical signals.

19:40 would it not be O/I instead of I/O? Anyways this answered a couple questions I had, especially the fact that we measure turbine discharge or thereabouts instead of jet nozzle discharge in which the pressure has already been turned into velocity.

I teach initial and recurrent training in the simulator for the venerable old Gulfstream IV (RR Tay; book value thrust 13,800lb). Engine thrust for this airplane is gauged via EPR, an indication as you say rather than a measurement of thrust. My question: is that EPR derived indication of thrust linear across the scale? That is, if the range of allowable thrust in flight goes from 1.0 to 1.6 EPR and the current thrust setting is 1.3 EPR does it follow that the engine is producing 50% of rated thrust (and by extension does 1.15 EPR = 25% and 1.45 EPR = 75%)? As you’ve pointed out in other videos, RPM and thrust are not linear but is that also true regarding EPR? Thank you!

Many times, instead of load cells that must be “between” the load and the anchor, they’ll use strain gauges to measure stresses (and therefore loads) in structures. I’m guessing that a problem with putting strain gauges on engine mounts is that they’re so strong that the don’t actually flex much so it might be difficult to get a useful reading out of them.

Damn blancolirio and all his gauges.👍👍

good vid dude

About 19:40 you show I/O = EPR. I think it should be O/I = EPR. Right?

Jerk question inbound: So EPR is basically the gas turbine equivalent for BMEP in piston engines in that they are both calculations?

Did you have to calibrate your test cell? That would be interesting!

… good videos… keep going …!!! 🙂👍

So in previous videos, we have well undestood that P9 has to be near to equal to P1 because there is nothing compressing the outflowing air besides the static air behind the turbine - so there can not be an overpressure other than caused by high speed air hitting slow/static air, or can there? P1 in your scheme seems to be a Pitot tube. How is P9 / P8 / P7 measured? If P9 is a Pitot tube as well we are basically comparing inlet air speed with outlet air speed - wouldn‘t that make sense? Of course it would make a difference if you compare inlet(ram)air pressure to pressure inside the turbine (where the air is actually confined).

0:40 I'm a jerk, my best friends are jerks. We have zero tolerance for stupidity. Maybe we should all get together and form a club.

Dear AgentJayZ, since you display a Rolls Royce Nene 10, could you explain that engine power control? Is it similar to the Ghost Haviland Mark IV? As a starter: Ghost MK4 controls the fuel delivery volume by two sensors, a barometric and a velocity pressure sensor. Could you explain how these to gauges control the fuel pump? Also that operation condition when the flames back fire?

Do you guys have an explanation for adaptive cycle engine

The heating failure in the shop brings a question to mind. We know that hot temperatures are not ideal for flying, but how much does ambient air temperature affect engine thrust, everything else being equal ?

'dohickies'- I didn't know Canadians had that term😆. A shout out for Gridlessness Homestead and Jadyn Rylee two other Canadians.

I the test cell, the instrumentation for force is just load cells isn't it?

Would not fuel use, give you an idea, on how hard you are going?

Thanks for all years of videos which was my guide in my job I would to ask and l hope to answer Since you are a test cell man , yesterday i was reading test cell performance and acceptance report for engine CFM56-5C engine and noted that 1- since the engine is a flat rated engine they test it with thrust higher than the actual thrust that i can gain in aircraft Its maximum thrust as CFM56-5C4 is 34000 pound but they test it at 35100 pound The question is all engine reading is now related to 351000 pound how can i know for example my actual (at thrust 34000) EGTM or N1&N2 vibration to decide the work wich has been done in the shop is accepted or not How can i get the data related to 34000 pound thrust

Turbochargers in aircraft? It sounded to me like you were describing an altitude compensation device, ... which of course it is.

i completed my assignment,, hope i get a gold star,,,,can you imagine what would happen to the thrust transducer as an aircraft lands? and ,, naaa your not a jerk,,

that was so funny man!!!! Thats right, Dads never wrong!!!!!!!!!!!!!!!!!

This is really cool. I am a young man who is very interested in jet aircraft ...... I hope that your videos will be translated into Arabic .... I want to ask what books do you recommend that are related to the field of jet engines for warplanes .... Thank you

There should be in every book published in North America a Copyright page, within the first Few pages, and you may find multiple references to different publishing's eg hard cover/ soft cover etc... and the multiple ISBNs relating to them. So your dad correct it would be a little easier , but that really only true if you cant operate google..

Strain gauge. A electro mechanical transducer measuring change in mechanical force.

Funny to think pressure load cells on a flying aircraft's engine mounts would just measure air resistance, but then you'd also know the thrust, all things being equal...

A shop full of jet engines but there's no heat. That's just little ironic if you think about it!

@23:22 The ISBN number is to the right of your thumb. To the right of the word "ISBN".

Surely there is a ‘heater’ that runs on natural gas somewhere in that shop lol

May be way off base here - but wouldnt a thrust gauge on an engine mount = zero. The gauges on the ground measure force in relation to the earth with they are effectively fixed to. There is an action/reaction equal an opposite on an engine mount unless accelerating.

I think you mean strain gauges, not stress gauges. Or am I a jerk ;-)

Load cell. The word you are trying to remember is Load Cell.

RPM is really a hell of a lot easier, and that is what GE uses~

You know, in a pinch, a jet engine can be used to make heat

Hello sir.. im wondering if you can explain how to trim a jet engine

19:28 P7. Well. Concorde had P7 gauge, but had no EPR indication. What was the actual purpose of installing P7 gauging system, other than providing input for takeoff monitor (that used P7 and FF as reference)?

Strain Gauges? That's what I call them.

EPR is the ratio of turbine discharge pressure to compressor inlet pressure. For example, an EPR of 2.0 means that the pressure at the turbine discharge is 2.0 times as great as the pressure at the compressor inlet. Or, it could be said that the pressure of the blow is 2 times greater than the pressure of the suck.

strain gauge?

Pilot's don't care about measuring thrust. If the airspeed is where you want it, power's good.

Boom, are trying to make a supersonic passenger aircraft but they don't have a suitable engine yet. They are aiming for mack 1.7 because any faster requires a movable intake cone to slow the intake air speed. Currently they are planning 4 engines Dose anyone have any ideas of what they can do? I think it's an interesting question at least. Can they adapt fighter jet engines or some existing engine. It has to be safe and reliable, capable of several flights a day. Noise restrictions will have to be considered if they want to fly over land to make it more commercially viable. Any ideas to save the project?

An engine mount designed to accommodate a strain gage? Needs to be flexible enough to deform the gage... you wouldn't want that flex in the aircraft...

We couldn't see the orange box hahahaaa

+1 for "doohickeys"

Voltage changes w pressure/lattice deformation of the material

.... strain gage

Thank Christ I only ever dealt with % rpm on the Viper 680. The test cell did all the calcs. We line engineers only had to get the max donk output speed within limits. Sooooooooooo much easier. Not that the Viper 680 Mk 43 was a friendly engine, though. Tempramental wee bugger that also burned the Mobil Jet 2 from the rear bearing. Nasty sh1t to breathe in, huh?

Recalibrate the micrometers...

there are no subtitles and i am a turkish what should i do for this problem please can you help me.

A vest and a hoodie , but no rona mask, aren't you in Canada ?

As an engineer even I find your explanations confusing and hard to follow. So much irrelevant information.