|
Talking of the U-2, did you know in the cruise the power was at idle.[/QUOTE]
Are you really sure. Sl 14.7 psi 70000 feet 0.6 psi I dont think the engine is at idle. It maybe making idle power at 70000feet but it most certainly would not be at the idle setting one would think. Maybe it turning at 2000rpm though. |
Flight manual.
With the P-37 engine an altitude will eventually be reached during the cruise climb where the engine is operating at idle RPM, the exhaust gas temperature is up to the rnaxirnum, and the aircraft is still climbing. When this condition occurs, prompt action must be taken to prevent over temperature operation of the engine. Initially, the condition may be corrected merely by allowing the aircraft speed to increase while maintaining constant altitude. When the speed has increased to a point within 5 knots of the needle, aerodynamic drag should be added. The initial drag is created by using the variable speed brake or extending the landing gear. As the aircraft descends, engine power is increased to maintain engine operation at maximum limitations. Eventually, the aircraft will cease descent and again begin a cruise climb. When the aircraft again reaches the altitude of limiting conditions, the remaining drag devices will be used. The P- 31 engine will normally never reach an altitude where idle RPM is encountered. However, maximum altitude is limited to the point where maximum exhaust gas temperature is reached and power cannot be further reduced without dropping below the minimum engine pressure ratio limit. The corrective procedure is the same as outlined above for the P·37 engine. |
Originally Posted by megan
(Post 10112749)
What our long departed and much admired 411A had to say.
Having flown DC-3's, DC-6's and Lockheed Constellations in the past, can say that ALL of these aircraft were climbed slightly high (100-200 feet), then descended slowly to the desired cruise altitude, while maintaining climb power. Once level at altitude, reduce to cruise power (approximately 50% BHP) and adjust mixture to autolean, close cowl flaps and oil shutters as needed...presto, time for coffee. ANY other method of level off at the desired cruise altitude took MUCH longer to reach the desired cruise speed, simply because these aircraft, as well as many older turboprops (F.27/FH227's for example) did not have excess power at higher altitudes, unlike many turbofan powered aircraft today. Focus on this part. ANY other method of level off at the desired cruise altitude took MUCH longer to reach the desired cruise speed Yes, if you leave in climb power, and/or dive slightly, you will achieve the maximum cruise airspeed sooner than if you level off and immediately set cruise power, and wait for it to build. When I was a flight engineer on the DC-6 I used to occasionally fly with a captain who would do that. Yeah, it took a long, long time to gradually accelerate to your cruising speed. And it was a real pain, because as an engineer, it really dragged out the time that you had to be constantly adjusting the cowl flaps and oil cooler door flaps to keep all your temps in line as airspeed soooooowly built. But for all that, eventually, you did reach the same cruising airspeed that you'd reach if you left in climb power and accelerated to slightly above it before setting cruise power. Once again, the "step climb theory" is the theory that by accelerating to a higher airspeed by diving or using climb power or both, you can you maintain a cruise airspeed higher than the *maximum* cruise airspeed you would get if you just accelerated to cruise airspeed with a lower power in level flight. |
Originally Posted by megan
(Post 10112905)
Flight manual.
The egine is not in idle. The engine has reached it critical engine operating limit. The power lever is not in idle. The power lever is forward of the idle position. The engine if it was in the idle positon would flame out. This is a totally different to what yo stated. The engine has the same thrust as at idle, it is not in idle. You dont seem to understand this. |
Looks like megan's found the same flight manual as me... later in the piece it goes on to say
An altitude will sometimes be reached where the minimum fuel flow setting equals that required for maximum exhaust gas temperature. This is called "minflow". In this case, retarding the throttle to idle will not change the power condition |
The min wf is set by the fcu compututing system. This will set max fuel per alt and position. Once again the engine is in its max crictal alt. The compututing section in the fcu will not be able to provide any more fuel. This is not as stated at idle. What it means is the engine is at its lowest self substaining level. Its not in the idle position in the compututing secting and there fore not in idle.
|
Originally Posted by Lookleft
(Post 10111853)
So my turn in opinion ping pong, from the above it can be taken that it is not an OWT.
I could be convinced that there is some effect out there which allows you to cruise at a measurable higher speed than your normal maximum cruising speed with the same power setting. It will take more than "some pilot said this is true" or "this guy who wrote some really popular aviation books said it was true" or "some guy on an internet forum claims he had a text half a century ago that explained this". What it would take is actual data, measured by some reputable and verifiable entity, together with some coherent explanation in aerodynamic terms of the nature of the phenomenon. So far that has been lacking here. |
In other words lest say idle n1 was 55%
One would imagine for n1 at 70000feet in this example would be 101% maxed out Clearly the engine is not idle. The crical thing now would be the itt or egt etc temp as the flow of air to fuel ratio will be the limiting factor. To stop this exceeding the temp they will have to drop of fuel which would put the engine below min fuel and therefore flame out. |
Originally Posted by Aussie Bob
(Post 10112132)
So I owned this early model 172, 6 cylinder Continental, 145HP @ 2600 RPM. From the placard on the engine: 145 HP @ 2600 135 HP @ 2500 etc. No rocket science required to work out that 100 RPM = 10 HP
|
One would imagine for n1 at 70000feet in this example would be 101% maxed out Clearly the engine is not idle. This is not as stated at idle. What it means is the engine is at its lowest self substaining level. Its not in the idle position in the compututing secting and there fore not in idle. |
Originally Posted by De_flieger
(Post 10112987)
Connedrod, you keep saying things like "one would imagine" and "one would think", but they are contradicted by a reliable reference, the operating handbook for the aircraft.
The flight manual says otherwise. According to the manual the power lever is either on or near the idle stop, reducing it onto the stop if not already there will not achieve a reduction in power and the fuel flow, EPR, NG and power being produced are all at their minimum levels. Sounds like idle to me. Are you saying n1 at idle at sl is the same n1 at 70000feet |
That's it. If that, in your mind is proof of anything, I think we've found the problem here. You have no idea what constitutes proof of anything. Until we have the information allegedly printed in those alleged texts, we really have nothing. As far as anonymous person's on the interent is concerned here is prof Dave Rogers bio: Dave Rogers is an airline transport rated pilot. He owns and flys a 1969 E33A Beech Bonanza. He has over 2300 flight hours and has been flying off and on for over 40 years. He was the chief pilot for the Naval Academy's flight test engineeing course. He habitually flys transcontinental, to Alaska, and to the Canadian High Arctic including as far north as Alert at 82 degrees 30 minutes. He has also flown across the North Atlantic in a single engine aircraft and thoughout the Carribean and the Bahamas. Dr. Rogers is a graduate of Rensselaer Polytechnic Institute where he obtained his Bachelor of Aeronautical Engineering, Master of Science in Aeronautical Engineering and Doctor of Philosphy in Aeronatical and Astronautical Engineering degrees. Professor Rogers was one of the original faculty who established the Aerospace Engineering Department at the U.S. Naval Academy in 1964. He has both an experimental and a theoretical research background. He has research interests in the areas of general aviation flight testing, hypersonic viscous flow, boundary layer theory, computational fluid mechanics, flight dynamics, highly interactive computer graphics, computer aided design and manufacturing, numerical control and computer aided education. He recently retired as Professor of Aerospace Engineering and Director of Aeronautics after 39 years of service. He has been honored with the title of Professor Emeritus. During his tenure he also served as Director of the Fluids Laboratories and head of the supercomputing group in addition to his professorial duties. Dr. Rogers is the author of five textbooks including An Introduction to NURBS, With Historical Perspective; Laminar Flow Analysis, Mathematical Elements for Computer Graphics, Procedural Elements for Computer Graphics, and Computer Aided Heat Transfer Analysis. He is also the co-editor of four books from the State-of-the-Art Series on Computer Graphics and the Proceedings of ICCAS 82 - the International Conference on Computer Automation of Ship Design and Ship Production. His books have been translated into six foreign languages. Over 100,000 copies of his books are in print. He has published over fifty technical papers and reports. He is a member of the American Institute of Aeronautics and Astronautics and ACM SIGGRAPH as well as a past member of the Society of Naval Architects and Engineers. Recently, one of his former students; Kevin Sharer, CEO and president of Amgen, endowed the David F. Rogers Chair in Aerospace Engineering at the United States Naval Academy in his honor. Dr. Rogers is the founder and former Director of the Computer Aided Design Interactive Graphics Group at the United States Naval Academy. He is series editor for the Springer-Verlag Series Monographs in Visualization and the founding editor of the journal Computers & Education. He also is a member of the editorial board of The Visual Computer and of Computer Aided Design. He is a former member of the AIAA Thermophysics TC and is currently a member of the AIAA Interactive Computer Graphics TC. He habitually serves on the technical program or organizing committees of both national and international conferences. Dr. Rogers was the Fujitsu Scholar at the Royal Melbourne Institute of Technology in Melbourne, Australia during 1987 and Visiting Professor at the University of New South Wales, Sydney, Australia in 1982. He was an Honorary Research Fellow at University College London in England during 1977-78 where he studied Naval Architecture with the British Royal Corp of Naval Constructors. actual data, measured by some reputable and verifiable entity, together with some coherent explanation in aerodynamic terms of the nature of the phenomenon. So far that has been lacking here. |
Originally Posted by Lead Balloon
(Post 10111109)
Aircraft that operate at sea level.
As you have no experience as a pilot, you’d not be aware that it’s possible to be operating at sea level so far as the engine is concerned, even though it’s higher than sea level. Indeed, it’s possible to be operating below sea level so far as an engine is concerned, and that’s where it’s particularly important to keep within the parameters in the engine limitations section of the flight manual/POH. No experience of any legal type, correct! So you now say "engine" !! Aircraft do not operate at sea level. On occasions the take off or fly in sea level conditions - but not at sea level, ground effect is close but not sea level. ** So your above and the corrected statement is correct. |
Originally Posted by travelator
(Post 10113025)
That is what the flight manual is being quoted as saying.
Whislt as you decrease fuel as you increase alt the compressor has to work hard to give you enough air to continue the cumbustion. Basic gas. Every gas turbine work on the same principles. The u2 is nothing special. The n1 at 70000 feet would be at or near max n1 and not at sl n1 speed. The engine will not work at sl n1 at 70000feet. My i suggest you go do basic gas N1 is the dead give away for engine profromance. It is one of the very first t hings that is looked at when a drop in power is detected. The higher the alt the faster for a give power setting the n1 must work, in other words whist at sl the n1 will give 1 to get to X whislt at 70000 it will have to work 24.5 times as hard to give X Idle will be a few % above self substaining that % is the same at alt but the compressor must work harder to maintain it ie an increase in n1 |
Originally Posted by Lookleft
(Post 10113027)
He wrote an article (the link was provided by megan) of why the step exists. |
So when are you going to provide the contrary evidence?
|
Tbm to get over this same problem use a engine that is rated near doulble the hp they require. Then derate that engine in half. Ie 1400 hp derated to 700 hp. This is so when it gets to its cruise alt it has sl profromance ie 700hp if it continues to climb the rated hp now decreases from 700 minus till it achives it selected alt. But as it increases its alt the n1 will increase wf will decrease as will itt. BGT .
|
LB
“Full Rich” isn’t “pure fuel”, is it? Full Rich is just the point on the lean curve that has been chosen as the mixture you get when the control is set there. |
Hi again oggers
When convenient: You want to run an engine at 74% power. What mixture do you set, by reference to peak EGT? Real world numbers please. At what mixture do you maximise the risk of detonation, all other variables like RPM, timing and manifold pressure being equal? A straight answer please. You’re the one flying all the precious passengers around each day. You must be setting the mixture somewhere, and doing so to avoid detonation? |
Originally Posted by Lead Balloon
(Post 10113280)
Hi again oggers
When convenient: You want to run an engine at 74% power. What mixture do you set, by reference to peak EGT? Real world numbers please. At what mixture do you maximise the risk of detonation, all other variables like RPM, timing and manifold pressure being equal? A straight answer please. You’re the one flying all the precious passengers around each day. You must be setting the mixture somewhere, and doing so to avoid detonation? So here is a few more for you i sure you can answer When you run lop at what point do you pass through the detenation range and how long are you there How many ga type aircraft run lop and how many run rop. Would you agree that more run rop than lop Please advise then we in the maintenance field arnt seeing damage to aircraft engines that run rop from detenation as you have discribed previously Please advise the folk here about what causes a burnt exhaust valve. Please advise what are the damage that is caused by detenation. Please advise what damage is cause by extreme leaning . What is the time limit for calibration of your edm instruments and conponents What is the reson for uneven breathing in aircraft engine cylinders What is the difference between gami fuel noz and old standard cont fuel nozzles Pleade advise the difference between a opposed engine in ga and a lagre radials that were used in a time since past. Please advise us of your maintenance experience and training and licence coverage. Thanks that do it for now. Lets see how you go. |
| All times are GMT. The time now is 06:08. |
Copyright © 2024 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.