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HowardDGA
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APU Thrust?

Wed Aug 10, 2022 5:59 pm

I could not find a topic about this, please redirect me if it has already been discussed.

Can APUs produce any meaningful thrust? And would it have any effect on an aircraft’s ETOPS certification?
 
nws2002
Posts: 999
Joined: Wed Feb 13, 2008 11:04 pm

Re: APU Thrust?

Wed Aug 10, 2022 6:05 pm

The only ETOPS effect I can think of is as another power source. No meaningful thrust to keep an aircraft aloft.
 
StereoTechque
Posts: 230
Joined: Sat Nov 28, 2015 7:24 am

Re: APU Thrust?

Wed Aug 10, 2022 6:34 pm

HowardDGA wrote:
Can APUs produce any meaningful thrust? And would it have any effect on an aircraft’s ETOPS certification?


Any little bit of thrust APU will produce is practically meaningless.
 
kalvado
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Joined: Wed Mar 01, 2006 4:29 am

Re: APU Thrust?

Wed Aug 10, 2022 6:40 pm

pretty long discussion: viewtopic.php?t=776251
Like always, there are some odd examples
 
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zeke
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Joined: Thu Dec 14, 2006 1:42 pm

Re: APU Thrust?

Thu Aug 11, 2022 7:54 am

HowardDGA wrote:
I could not find a topic about this, please redirect me if it has already been discussed.

Can APUs produce any meaningful thrust? And would it have any effect on an aircraft’s ETOPS certification?


Short answer is the APU will not produce propulsive thrust to move the aircraft forward, however the APU bleed can be used to drive the packs, this can provide more available thrust from the engines.
 
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HowardDGA
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Re: APU Thrust?

Thu Aug 11, 2022 8:02 am

kalvado wrote:
pretty long discussion: viewtopic.php?t=776251
Like always, there are some odd examples

Thank you, that is an interesting thread.
 
Natflyer
Posts: 716
Joined: Fri Oct 11, 2013 9:29 pm

Re: APU Thrust?

Thu Aug 11, 2022 10:52 pm

HowardDGA wrote:
I could not find a topic about this, please redirect me if it has already been discussed.

Can APUs produce any meaningful thrust? And would it have any effect on an aircraft’s ETOPS certification?


I heard that question asked by a colleague years ago in ground school.

About 3 knots. Per year. Was the instructors reply.
 
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Starlionblue
Posts: 21183
Joined: Fri Feb 27, 2004 9:54 pm

Re: APU Thrust?

Fri Aug 12, 2022 5:19 am

Does the Trident Three's fourth engine count? 8-)

Image


Also... Insert joke about the BAe-146/Avro RJ, whose engines are derived from an APU.
 
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zeke
Posts: 17398
Joined: Thu Dec 14, 2006 1:42 pm

Re: APU Thrust?

Fri Aug 12, 2022 10:22 am

Starlionblue wrote:
Does the Trident Three's fourth engine count?


That was a takeoff engine, the RB162, gave about 5000 lb of thrust for takeoff and shutdown after 5 minutes.

The APU on that aircraft is located above the “trident” above the engine 2 intake
 
hitower3
Posts: 306
Joined: Fri Oct 21, 2016 9:55 am

Re: APU Thrust?

Fri Aug 12, 2022 12:03 pm

I vaguely remember having seen a concept of an enlarged APU being able to provide a limited amount of additional thrust for a twin engine jet.

The idea was to slightly bump the MTOW under consideration of a failure of one main engine.

Best regards,
Hendric
 
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Starlionblue
Posts: 21183
Joined: Fri Feb 27, 2004 9:54 pm

Re: APU Thrust?

Fri Aug 12, 2022 12:14 pm

zeke wrote:
Starlionblue wrote:
Does the Trident Three's fourth engine count?


That was a takeoff engine, the RB162, gave about 5000 lb of thrust for takeoff and shutdown after 5 minutes.

The APU on that aircraft is located above the “trident” above the engine 2 intake


I know. I know.

But one should never forgo the opportunity to mention British aircraft design weirdness, no matter how tenuous the connection. :biggrin:
 
26point2
Posts: 1156
Joined: Wed Mar 03, 2010 6:01 am

Re: APU Thrust?

Fri Aug 12, 2022 12:50 pm

The GLEX actually has a performance penalty with APU running due the the retractable APU inlet door which creates some drag.
 
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Classa64
Posts: 370
Joined: Fri Apr 03, 2015 5:40 pm

Re: APU Thrust?

Sat Aug 13, 2022 8:29 pm

kalvado wrote:
pretty long discussion: viewtopic.php?t=776251
Like always, there are some odd examples


The first time in months I visit the Tech/Ops section and the same question I asked 6 years ago is in the top 5.

Funny
 
Natflyer
Posts: 716
Joined: Fri Oct 11, 2013 9:29 pm

Re: APU Thrust?

Sun Aug 14, 2022 2:38 pm

Starlionblue wrote:
zeke wrote:
Starlionblue wrote:
Does the Trident Three's fourth engine count?


That was a takeoff engine, the RB162, gave about 5000 lb of thrust for takeoff and shutdown after 5 minutes.

The APU on that aircraft is located above the “trident” above the engine 2 intake


I know. I know.

But one should never forgo the opportunity to mention British aircraft design weirdness, no matter how tenuous the connection. :biggrin:


Very true!

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