Engines thrust power reduction

Sustainable airplanes are airplanes with minimal entropy production and maximal efficiency. Simple way to express the entropy law is that in an airplane all components and subsystems tend to disintegrate. The break, break down, break up, friction, cavitation (or nucleate boiling, or fuel weathering), chemical reactions, water production from hydraulic oil and fuel, rust, die, decay, wear out, fuel tank explosions, aircraft engines thrust power reduction, roll back and/or shut down, and generally move from a state of higher organisation to one of lower organisation, from order to chaos. An airplane is in a critical high entropy state if very small perturbations induce an answer of the system at all time and space scales.

"Absolute" fuel and hydraulic oil filtration techniques have become an important operation in aviation. One of the major concerns in he "absolute" fuel filtration is the entropy generation on the membrane surface. During the filtration both the fuel and hydrauli oil have a natural tendency to undergo irreversible processes and thereby increase the entropy of an
airplane.

The cause: ice on wings or entropy in a fuel tank?

Ice on wings? . . .
The business jet twin engine Canadair Challenger, a CL-600 (N873G), impacted a fence and terrain off the departure end of runway 31 at approximately 9:55 a.m. November 28, 2004 while attempting to take off from Montrose Regional Airport, Colorado, USA. A post-crash fire ensued. The two pilots were killed and a passenger is missing. The recent takeoff accident that has generated much discussion about the effects of wing upper surface ice accumulations. The National Transportation Safety Board has long been concerned about the insidious nature of the effects of small amounts of ice accumulated on an airplane's upper wing surface. Research results have shown that fine particles of frost or ice, the size of a grain of table salt and distributed as sparsely as one per square centimeter over an airplane wing's upper surface can destroy enough lift to prevent that airplane from taking off. Research has shown that almost imperceptible amounts of ice on an airplane's wing upper surface during takeoff can result in significant performance degradation. Ice accumulation on the wing upper surface is very difficult to detect. It may not be seen from the cabin because it is clear/white and it is very difficult to see from the front or back of the wing. The Safety Board believes strongly that the only way to ensure that the wing is free from critical contamination is to touch it. Accident history shows that nonslatted, turbojet, transport-category airplanes have been involved in a disproportionate number of takeoff accidents where undetected upper wing ice contamination has been cited as the probable cause or sole contributing factor. The industry acknowledges that it is nearly impossible to determine by observation whether a wing is wet or has a thin film of ice.

...or entropy in a fuel tank?
Strict attention should be focused on ensuring that fuel entropy in a tank is minimal at the initiation of takeoff. The detection of entropy in the fuel, sufficient to cause engine thrust power problems, is difficult and may not be possible without a measuring instrument. Strange as it may seem, entropy will have a tremendous effect on reducing the performance of a modern airplane. Despite the accident and research evidence indicating that small imperceptible amounts of entropy can cause the same penalties as ice accumulations. Recent accidents indicate that the pilot community still may not appreciate the potential consequences of small amounts of entropy in fuel. However our research has shown that small amounts of entropy can result in considerable engine thrust power degradation. It is possible that many pilots believe that they have sufficient engine power available, they can simply "power through" any performance degradation. However, unsufficient engine power will not prevent a stall and loss of control at lift off. Also it is critically important to ensure, by any means necessary, that the fuel in tank is clear of entropy before takeoff.

[edit on 28-9-2005 by elpasys]

The United Airlines Boeing 767 Flight 42, March 4, 2001.
On March 4, 2001 a United Airlines Boeing 767, Flight 42, departing from Maui, Hawaii experienced a dual engine roll back due to nucleate boiling of fuel. The initial readout of the Flight Data Recorder (FDR) indicates that, while climbing through 29,000 feet, the right engine experienced a reduction in power to below idle but did not completely stop operating. About 20 seconds later, the left engine experienced a similar reduction in power. The reduction of power occured as the crew attempted to rectify an imbalance in the fuel load. Approximately 20 seconds after the power reduction in the second engine the FDR stopped recording data for a period of time no greater than half a minute. There is no indication that the airplane, its engines or systems malfunctioned. What went wrong?

After reading the NTSB's report on the Canadair Challenrer crash I don't think that icing on the wing was the problem. The NTSB report doesn't have a cause listed for the accident.
NTSB on Canadair Challenger

The report mentions witnesses hearing a loud Boom or Woosh before the crash. To me, these sounds give me the impression of an engine problem or flameout. This could be caused by fuel contaminated with water that froze into ice and clogged the fuel line. If this happened on only one engine the resulting loss of power and assymetrical thrust combined with weather conditions could have caused this crash.

I am kind of curious about what you mean by the term "entrophy"? As I understand it entrophy is the tendency of organized items becoming disorganized through natural actions. How does this pertain to aircraft fuel tanks? If my definition of entrophy is wrong please correct me.

Entropy: the ultimate, most pervasive and destructive law of Nature.

Originally posted by elpasys
Entropy: the ultimate, most pervasive and destructive law of Nature.

Main Entry: en·tro·py
Pronunciation: 'en-tr&-pE
Function: noun
Inflected Form(s): plural -pies
Etymology: International Scientific Vocabulary 2en- + Greek tropE change, literally, turn, from trepein to turn
1 : a measure of the unavailable energy in a closed thermodynamic system that is also usually considered to be a measure of the system's disorder and that is a property of the system's state and is related to it in such a manner that a reversible change in heat in the system produces a change in the measure which varies directly with the heat change and inversely with the absolute temperature at which the change takes place; broadly : the degree of disorder or uncertainty in a system
2 a : the degradation of the matter and energy in the universe to an ultimate state of inert uniformity b : a process of degradation or running down or a trend to disorder
3 : CHAOS, DISORGANIZATION, RANDOMNESS
- en·tro·pic /en-'trO-pik, -'trä-pik/ adjective
- en·tro·pi·cal·ly /-pi-k(&-)lE/ adverb

I took this definition from Merriam-Webster's on line dictionary. I am still having problems with figuring out how you came about your definition.

I don't really understand the thread...

Entropy occurs in a thermodynamic process, and is essentially wasted heat.

An aircraft crashed because of possible ice accumulation on the wings... or...???

Increased fuel temperature? Blockages in the fuel lines? Change in chemical composition of the fuel? I don't understand what you are trying to say.

Originally posted by kilcoo316
I don't really understand the thread...

Entropy occurs in a thermodynamic process, and is essentially wasted heat.

An aircraft crashed because of possible ice accumulation on the wings... or...???

Increased fuel temperature? Blockages in the fuel lines? Change in chemical composition of the fuel? I don't understand what you are trying to say.

kilcoo316 you're in the same boat that I am. I think that elpasys may have an interesting theory, but we may have a language barrier problem. He posted the initial information about the aircraft incidents. I was able to find the NTSB report on the Canadair accident and while it gave the weather conditions favorable for icing it didn't list it as a possible cause. By the information in the report I brought up the idea of ice in the fuel blocking the fuel lines. I asked elpasys what he considered the definition of entropy to be. I couldn't understand his definition so I posted one from a dictionary. I would like to find out what he is referring to but like I said we may have a language barrier problem

In fuel a concept called entropy that is a measure of the amount of energy no longer capable of conversion into work in an engine. It is thus measure of the unavailability of energy dissipated (exergy loss) in the fuel. Exergy of the fuel, once destroyed, is unavailable to perform further work. Entropy can also be shown to be a measure of the level of disorder of an airplane.

Thermodynamic potential: G=U+pV-Tam(Sf+Sv+Sa) [1]

where: G-Gibbs potential (free ehthalpy), U-internal energy, p-fuel pressure, V-fuel volume, Tam-ambient temperature, Sf-fuel's entropy, Sv-vibrational entropy, Sa-acoustic entropy

The destroyed exergy, or the entropy generated within the fuel is responsible for the less-than-theoretical efficiency of the engine. Large quantities of entropy are created during refueling. Due to entropy production the thermodynamic potential [1] of the engine is zero when it is in final equilibrium with the environment (thrust power = zero). The thermodynamic potential of an airplane in operatin becomes lower and lower. Deterministic chaos is only one possible consequence, form of self-organisation in which there is an overload of entropy. The problem is that when we destroy the exergy in the fuel we add internal energy (because T increase), and we also add entropy (because S increase). If we want to continue using an engine to do work, we have to remove the entropy from the fuel, so there is no accumulation of entropy in the fuel.

Fuel tank system of many interacting fuel particles with a relatively high entropy exibit phase transition between high entropy state and a low entropy state with a core-halo structure (bubbles formation). During such a transition entropy has to undergo a discontinous jump from a state a local entropy maximum to a state with different temperature, which is the global entropy maximum. Consequence: nucleate boiling, cavitation, and fuel gasification before the pump.

Entropy, the biggest problem of aviation, is my theory.

Ice on wings as a cause of problems during take-off is well known theory, see: "Alert to Pilots: Wing Upper Surface Ice Accumulation", NTSB Advisory, December 29, 2004.

The Challenger jet crash in Teterboro, New Jersey, February 2, 2005. (see: NTSB Advisory, February 2, 2005).

On February 2, 2005, in Teterboro, New Jersey, a Bombardier Challenger CL-600 corporate jet overran the departure end of runway 6 during an aborted takeoff attempt and crashed into a fence, two cars, and a warehouse. A postcrash fire ensued. The pilot, copilot, and two automobile occupants received serious injuries, and a cabin aid and eight passengers received minor injuries. The accident occurred about 7:17 a.m. Visual meteorological conditions prevailed at the time of the accident. Preliminary evidence indicated that icing conditions at Teterboro were minimal or non-existent on the morning of the accident. The airplane did not pitch up during takeoff, even though the airplane was traveling at a high speed. Upper wing ice contamination has not been associated with the inability of an airplane to pitch up for takeoff; rather, upper wing ice is typically associated with the inability of an airplane to fly after it has pitched up to a takeoff attitude.

The operations and performance groups have conducted tests using a simulator to evaluate the airplane's takeoff characteristics based on the trim settings and weight and balance data. The initial findings of those simulations indicate the airplane would not rotate for take off at the defined rotation speed. Engine examination, FDR data, and flight crew and eyewitness reports indicated that the engines functioned as expected(???). The FDR operated for only about 10 seconds, starting when the airplane was decelerating through 153 knots and ending when the airplane had slowed to 91 knots.

Edit: cosmetics

[edit on 30-9-2005 by elpasys]

The aircraft had got up to speed elpasys, so the engines were working at the initial flight stages.

Your saying movement in the fuel will reduce its energy levels, thats true since:

- air bubbles may be created lowering actual fuel:air mix ratio in combustion chamber.

- fuel temperature will rise as a result of viscosity, lowering combustion efficiency.

However, I would assume the fuel pump would be strong enough to minimise the formation of bubbles into the engine to virtually insignificant levels, and the rise of temperature of the fuel is miniscule compared to the 1400 degree kelvin of the combustion chamber.

A far more likely explanation in my opinion would be contamination of the fuel, which affected the fuel pump or blocked the lines.

If entropy was such a large problem, surely it would have occurred more often throughout aviation history and would be well understood by now

Yeah, if entropy was responsible for all these crashes then there would be a MUCH bigger understanding of the effects, and they would have found a way to solve, or alleviate the problem by now. The FAA doesn't move fast, but you'd think that entropy would have been going on from the start of aviation if it was going to be a problem, and not even the FAA moves THAT slowly.

Exergy analysis can reveal how is possible to design more efficient aircraft. We cannot continue in our present methods of using the aiplanes. Life is a system in steady-state thermodynamic disequilibrium that maintains its constant distance from equilibrium (death) by feeding on low entropy from its environment-that is, by exchanging high-entropy outputs for low entropy inputs. The same statement would hold verbatim as a physical description of an aircraft. A corollary of this statement is that an organism (or an aircraft) cannot live in a medium of its own waste products (entropy = wasted energy).

We made an attempt to apply chaos theory to the airplanes. But the consensus of expressed opinion is still against any solution of the entropy problem in the aviation and space. Thus currently in the aviation sectors prevailing the non-sustainable trends, mankind versus Mother Nature.

Directions against entropy and chaos(???): NTSB Safety Recommendations.
National Transportation Safety Board, March 08, 2005
Safety Recommendations A-05-03 through –07

The National Transportation Safety Board recommends that the Aviation Administration: Require Honeywell to modify its flight management system (FMS) software to annunciate warnings to the flight crew when a takeoff reference speed is changed by a value that would impede the airplane's ability to safely take off, and require all operators of airplanes with Honeywell FMS computers to incorporate this software modification. (A-05-03)

Require Honeywell to modify its flight management system (FMS) software to prevent entry of airplane weights that would result in landing weights below zero fuel weight or operating empty weight, and require all operators of airplanes with Honeywell FMS computers to incorporate this software modification. (A-05-04)

Require Honeywell to modify its flight management system (FMS) software either to inhibit manual entries in the gross weight field or to allow the takeoff gross weight to be uplinked directly into the FMS, and require operators of airplanes with Honeywell FMSs to incorporate this software modification. (A-05-05)

Require Honeywell to conduct a study of its flight management system computers to identify any additional improvements that may be necessary for error checking and confirming that the entered takeoff and landing performance information is correct and reasonable. (A-05-06)

Require companies other than Honeywell that manufacture flight management systems (FMS) that are installed on 14 Code of Federal Regulations Part 25 airplanes to study their FMS computers to identify any improvements that may be necessary for error checking and confirming that the entered takeoff and landing performance information is correct and reasonable. (A-05-07)

I think that I have a handle on what elpasys is saying.
This is my interpretation so please forgive or feel free to correct any errors that I might make.

What I think he is trying to do is to apply chaos theory to the fuel effiency of jet engines. Less than optimum fuel temperatures, air bubbles, cavatation and contamination all tend to reduce the effiency at which the engine converts the energy stored in the fuel to usable energy. The application of the word entropy is meant to apply to the natural tendency of objects that are in order to become disordered unless acted upon by an outside force. It is considered a law of thermodynamics that for every change of state there are losses. In my opinion elpasys is stating that entropy is responsable for some of these losses. While I have to agree with him I also have to add that modern jet engines are designed with these losses in mind and account for them during operation.

As far as ice build-up goes, it has been known for a long time that the build-up of even minor amounts of ice can alter the effiency of aircraft wings. Modern airfoils are designed to operate at maximum effiency for both performance and economy. Minor changes to that airfoil, in the form of ice build-up, wing damage or other causes can reduce the capability of the wing. I remember reading about the crash of that Challenger. I think that one of the items brought up was that the flight crew didn't get out of the aircraft and do another preflight before taking off. They also didn't request that deicing fluid be sprayed on the wings. If they had an engine problem on takeoff and there was enough ice on the wings to degrade their performance, these events combined could have caused the crash.

Originally posted by elpasys
NTSB Safety Recommendations.
National Transportation Safety Board, March 08, 2005
Safety Recommendations A-05-03 through –07

The National Transportation Safety Board recommends that the Aviation Administration: Require Honeywell to modify its flight management system (FMS) software to annunciate warnings to the flight crew when a takeoff reference speed is changed by a value that would impede the airplane's ability to safely take off, and require all operators of airplanes with Honeywell FMS computers to incorporate this software modification. (A-05-03)

Require Honeywell to modify its flight management system (FMS) software to prevent entry of airplane weights that would result in landing weights below zero fuel weight or operating empty weight, and require all operators of airplanes with Honeywell FMS computers to incorporate this software modification. (A-05-04)

Require Honeywell to modify its flight management system (FMS) software either to inhibit manual entries in the gross weight field or to allow the takeoff gross weight to be uplinked directly into the FMS, and require operators of airplanes with Honeywell FMSs to incorporate this software modification. (A-05-05)

Require Honeywell to conduct a study of its flight management system computers to identify any additional improvements that may be necessary for error checking and confirming that the entered takeoff and landing performance information is correct and reasonable. (A-05-06)

Require companies other than Honeywell that manufacture flight management systems (FMS) that are installed on 14 Code of Federal Regulations Part 25 airplanes to study their FMS computers to identify any improvements that may be necessary for error checking and confirming that the entered takeoff and landing performance information is correct and reasonable. (A-05-07)

Thats all for human error related problems!

Originally posted by elpasys
Exergy analysis can reveal how is possible to design more efficient aircraft. We cannot continue in our present methods of using the aiplanes. Life is a system in steady-state thermodynamic disequilibrium that maintains its constant distance from equilibrium (death) by feeding on low entropy from its environment-that is, by exchanging high-entropy outputs for low entropy inputs.

The same statement would hold verbatim as a physical description of an aircraft. A corollary of this statement is that an organism (or an aircraft) cannot live in a medium of its own waste products (entropy = wasted energy).

We made an attempt to apply chaos theory to the airplanes. But the consensus of expressed opinion is still against any solution of the entropy problem in the aviation and space. Thus currently in the aviation sectors prevailing the non-sustainable trends, mankind versus Mother Nature.

I think maybe your making a bad application of a theory here I would guess the number of aircraft failures that have resulted from chaos theory in this context are... well... are probably 0

So what would you suggest as solutions to the problem?

I give up! I haven't a clue as to what he's talking about. I'm getting a headache just trying to start to figure it out. I think that he is saying that we should ban aircraft, because every so ofter someone gets killed.

December 12, 2001, Indian Ocean.
The B-1B bomber crashed after refueling into the Indian Ocean. The aircraft was "impossible" to fly, said the plane's rescued pilot. The four crew members declared an emergency about 15 minutes before ejecting from an altitude of 15,000 feet. Sign of chaos: "the aircraft was out of control and we all had to eject; we had multiple aircraft system malfunctions, which made it impossible for us to fly the aircraft." The pilot said: "the problems were not a result of enemy fire" - sooner a result of high entropy. A USAF KC-10 refueling plane orbited the crash site, maintaining voice communication and visual contact with the B-1B crew. Officials would not comment on the bomber's mission or destination.

Entropy won.

Again, entropy had nothing to do with it. The B-1 can be a piece of crap to fly, and one minor problem can rapidly become one major problem. The wound up with FOUR major problems, including a fire, ending with them going out of control.

You seem to skip over the parts that disagree with you, or find other reasons for the cause to show that entropy caused it.

On January 13, 1982, Air Florida Flight 90, a Boeing 737-222 (N62AF) was a scheduled flight to Fort Lauderdale, Florida, from Washington National Airport, Washington, D.C. The scheduled departure time was delayed about 1 hour 45 minutes. The aircraft took off in heavy snow. The tower lost sight of Palm 90 during it's roll due to the reduced visibility, but radar showed it airborne and the tower controller instructed Palm 90 to contact the departure controller. Less than a minute after taking off, Palm 90 descended at low airspeed into the Rochambeau bridge and plowed through into the Potomac river, 0.75 nmi from the departure end of runway 36.

Beginning information gave evidence of airframe icing, but further analysis showed other probelms with Palm 90. Shortly before takeoff, the crew have a brief discussion concerning anomalies in the engines. The indications seemed to return to near normal as Palm 90 got closer to takeoff. As Palm 90 was cleared for takeoff, the pilot remarked at the abnormal indications from the engines again. During takeoff the the aircraft was not accelerating properly due to fuel's entropy. The aircraft traveled almost 1/2 mile (800 m) further down the runway than is customary before liftoff was accomplished. Still, 45 seconds into the takoff roll, Palm 90 reached it's rotation speed and pitched up abruptly. Survivors indicated the trip over the runway was extremely rough, one of whom admitted he feared that they would not get airborne and would "fall off the end of the runway."

Although the aircraft did manage to become airborne, it failed to gain altitude, then the stall warning came on, "Forward! Forward!", indicating to lower the nose to prevent the stall. and. The aircraft remained airborne for only 30 seconds. The pilot believed that the engines were producing max thrust during takeoff.

The CVR recording ended with the crew's final acknowledgement of the severity of their situation. "Larry-we're going down Larry!". "I know it!".

There were 74 passengers, including 3 infants, and 5 crew members on board. Only six people survived.

The National Transportation Safety Board determines that the probable cause of this accident was the flight crew's failure to use engine anti-ice during ground operation and takeoff, their decision to take off with snow/ice on the airfoil surfaces of the aircraft, and the captain's failure to reject the takeoff during the early stage when his attention was called to anomalous engine instrument readings(!).

It's called ICE> They failed to deice the wings between the first deicing, and the time of take off which was something like an hour later. Again, no entropy, just human error.

Originally posted by elpasys
The probable cause of this accident was the captain's failure to reject the takeoff during the early stage when his attention was called to anomalous engine instrument readings(!).

See: [url=http://www.ntsb.gov/publictn/1982/AAR8208.htm[/url]