Talk:Auxiliary power unit

APU Fuel
From my little experience, I know that the when an aircraft is in the cold and dark state, you have to ensure that all crossfeed valves are open but you have to make sure all the fuel pumps are off. Does this mean that the APU has its own separate fuel tank or does the fuel just flow to the APU because of gravity?

Ans: Not sure what aircraft you are talking about. The start sequence for most APUs automatically positions valves and energizes the appropriate aircraft fuel pump(s) prior to starter rotation. Depending on aircraft make and model, the APU is fed by pressure pump or eductor from either a main wing tank, or a collector tank often located in the fuselage (typical of some regional jets). The APU does not have its own fuel tank. The APU also has a fuel pump driven off the accessory gearbox that provides high pressure fuel required to produce atomized spray patterns from the fuel nozzels. Gravity feed would not likely provide adequate fuel pressure to the APU fuel pump that could result in cavitation or starvation.

Truck APUs
"currently the most common APU units for Highway trucks are; Wabaso, Proheat, and Espar."

these aren't APUs, they are actually diesel-fired heaters. As for the most common APU, I've seen more Thermo King TriPacs on trucks than any other make in my time on the road.--Lpimlott (talk) 04:28, 1 November 2009 (UTC)

Changing the "Other" Category for Truck APU's
I would like to change the name of the "Other" category to "Fuel Cells" and update the information there. Since there are only 2 sentences there now, I would just replace those with the following...

In recent years truck and fuel cell manufacturers have teamed up to create, test and demonstrate a fuel cell APU that eliminates emissions and uses diesel fuel more efficiently. In 2008, a DOE sponsored partnership between Delphi Electronics and Peterbilt demonstrated that a fuel cell could provide power to the electronics and air conditioning of a Peterbilt Model 386 under simulated "idling" conditions for 10 hours. Delphi has scheduled the 5 kW system for Class 8 trucks to be released in 2012, at a $8000-9000 price tag that will be competitive with other "midrange" APU's. Benfchea (talk) 16:03, 23 September 2011 (UTC)

Anti-swedish bias complained.
The military aircraft section of this article is totally false. The swedish JAS-39 Gripen, the most petite supersonic fighter jet of this era, has a full airliner style APU. It's a small turbine engine made by Sundstrand-Hamilton, that gives her complete autonomy on the tarmac (or the autobahn): starts propulsion, sustains full avionics and comms while idling for an alert, facilitates in-flight propulsion restart in case of FOD or flame-out incident, etc. The F-15, F-16 have nothing like that kind of autonomy, as they depend on an APU truck. If they start without an APU, only "ferry/skeleton" avionics will be available, with no combat functionality at all. 87.97.98.5 (talk) 20:36, 30 December 2011 (UTC)

Main image
The best picture we have is an exhaust? SChalice 19:20, 1 February 2012 (UTC)

Why limit APUs to turbines?
Using the first sentence of the initial paragraph as a definer, there's nothing that says APUs have to be small gas generators (turbines), or that the C-124 was the first military airplane with an APU. Plenty of large military aircraft--B-29, B-17, all the way back to the PBY--had on-board power units to drive a generator and supply electricity when the engines weren't running. Some of them were even started with pull-cords, like a lawnmower, but they definitely were sources of auxiliary power even though they were gasoline-powered reciprocating engines, both two- and four-cycle. 173.62.11.221 (talk) 21:33, 8 April 2012 (UTC)

First Military Aircraft with an APU
There seems to be a bit of confusion on "first" military aircraft with an APU:
 * The C-124 article states that it was the the first military aircraft with an APU.
 * This is incorrect if one is to believe this article, which states that the Me 262 was the first military aircraft with an APU.
 * This article states that the C-124 is the first American military aircraft with an APU.
 * This is also incorrect if one is to believe the YFM-1 article.
 * Although it might make the C-124 the first operational American military aircraft with an APU.
 * Except the source given for the C-124 makes no claim to either of the "firsts" mentioned above.
 * However, if one believes the YFM-1 article, then the (unsourced, I might add) Me 262 claim made on this article is also incorrect as the YFM-1 was built in 1937.
 * The same qualification about "operational" could be made for the 262 claim as was made for the 124; as well as an additional one for being the first jet.

So we seem to be at a quandary. And seeing as I have no idea as to which, if any, of the above claims are actually true, I am not of much more help. Can anyone who is at least some sort of an authority on the matter try to clear this up? --Noha307 (talk) 01:19, 9 August 2012 (UTC) (Edited at 1:30)


 * After reading more of the article (and the above section, duh!), it appears that some of the confusion might stem from what is defined as an APU. --Noha307 (talk) 01:40, 9 August 2012 (UTC)
 * Try Supermarine Nighthawk for a really early APUNigel Ish (talk) 07:48, 9 August 2012 (UTC)


 * It is not unusual to find qualified claims (like first operational APU) or even different references making conflicting claims. As per WP:V we have to go with what the refs actually say and if they conflict then either remove all the claims, or, more usually, indicate the conflict of sources and cite the conflicting ones to explain the controversy. - Ahunt (talk) 13:08, 9 August 2012 (UTC)


 * For the time being I'll remove the Me-262 claim, since it's unsourced, and replace it with the Supermarine Nighthawk claim. --Noha307 (talk) 19:16, 14 August 2012 (UTC)

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