CPH-R
Topic Author
Posts: 6164
Joined: Thu May 03, 2001 5:19 pm

Concorde Eng #4

Wed Feb 13, 2002 5:27 am

I've just watching through the Just Planes' Concorde video, and I'm now in the second part.

Now, the FE has just said that the number 4 engine goes at a slightly lower RPM than the rest, on take-off.

What's up with that?
 
Beefmoney
Posts: 1071
Joined: Tue Oct 10, 2000 2:16 am

RE: Concorde Eng #4

Wed Feb 13, 2002 8:22 am

Well, I fly small cessna's so Im not an expert o the Concorde, but...... When the blades are spinning in the engine, clockwise I assume, it creates torque, which causes a tendancy for the airplane to turn and yaw to the left. Now with the tremendous amount of tourque that could be created by the Concordes very powerful engines, you may need somthing to counter act that. That us why I am guessing the have a lower power setting on the #4 engine during takeoff, so that they will have more power on th left side to offset the torque.
Anyway, my $.02
 
jsuen
Posts: 204
Joined: Tue Aug 14, 2001 2:36 pm

RE: Concorde Eng #4

Wed Feb 13, 2002 10:31 am

I don't think it has to do with the torque, you would have a greater problem with a 747. Takeoff thrust on the Concorde is only about 38,000 lbs per engine.

It probably has to do with using bleed air from the no 4 engine. Several airliners do that. For example, the 727 does not bleed as much air from the no 2 engine, and consequently its speed is slightly higher.
 
B1C17L1011
Posts: 96
Joined: Fri Jun 29, 2001 12:42 am

RE: Concorde Eng #4

Wed Feb 13, 2002 11:54 am

I saw a video of concorde taking off and noticed that the #4 engine reached full after-burner a few seconds later than the other three which lit simultanously. You could see the pilot correcting with a left rudder imput as the tail moved.


Any answers.
 
Beefmoney
Posts: 1071
Joined: Tue Oct 10, 2000 2:16 am

RE: Concorde Eng #4

Wed Feb 13, 2002 1:00 pm

Jsuen- You are probably right, after all, I know that jets dont produce as much torque as my cessna, but that was the only thing I could place as a reason for the power reduction. It couldnt be an airflow problem because that would occur on the #1 engine as wel. So it would have to do with some internal component that needs less or doesnt need as much power/bleed air etc.. to run properly. CPH-R- Did he say this was the case with all concordes, or just with this particular one? If it was just the specific one, it could be because the #4 engine is newer thatn the rest and can output more power. What are your thoughts on this?
 
musang
Posts: 792
Joined: Sun Apr 08, 2001 4:11 am

RE: Concorde Eng #4

Wed Feb 13, 2002 7:19 pm

Hello CPH-R, here's the reason.

The engine intakes are angled slightly towards the fuselage centreline, so as to align with the airflow at supersonic speeds. The lower the speed, the further from aerodynamic perfection they are, as the air going into the intake is forced to change direction slightly. This causes slight vibration, as the air doesn't meet the compressor first stage (N1) head on.

The situation is complicated by the fact that the engines all rotate the same way, as you'd expect. The relationship between the air going into the No. 1 intake, and its engine, is therefore slightly different from the situation at No. 4. (and No. 2 vs. No. 3). Due to the spanwise airflow, in other words the left/right component of the stream, which is different from that at supersonic speeds, and different for each intake in relation to its compressor, the mismatch at No. 4 four is the greatest.

That was a bit wordy, so here it is from the (British) Chief Test Pilot - "the effect on the blade vibrator modes is markedly different for each engine" (quoted from Brian Trubshaw's book Concorde - The inside Story, page 44). "So much so that the N1 on engine 4 is automatically held down up to 60 knots, when it is released".

So at 60 knots, the No. 4 intake is judged to be feeding air to its engine at an angle acceptable to the fan, and the vibration is less of a problem.

Torque is insignificant on jets, and any bleed air off-take, generator or hydraulic pump loading would be compensated for by the fuel control unit so as to keep the thrust up to the required level.

Regards - Musang
 
CPH-R
Topic Author
Posts: 6164
Joined: Thu May 03, 2001 5:19 pm

RE: Concorde Eng #4

Thu Feb 14, 2002 10:32 am

Thanks (again) Musang

I had some wild theory myself, that it might be due to the take off procedure from 31L at JFK, which requires the Concorde to make a hard left turn right after PRC is achieved. This turn would, of course, be much easier if differential thrust was used.

Which reminds me: How come there are very few shots of aircrafts on the Canarsie approach to 31L/R at JFK? IT ought to be interesting enough!
 
lmml 14/32
Posts: 2358
Joined: Tue Jan 30, 2001 2:27 am

RE: Concorde Eng #4

Tue Feb 19, 2002 7:56 pm

Are the afterburners engaged by advancing the throttles to the corresponding detent or is there another "switch"? Does Concorde have autothrottle? And is the IRS different due to the high speeds?
 
musang
Posts: 792
Joined: Sun Apr 08, 2001 4:11 am

RE: Concorde Eng #4

Tue Feb 19, 2002 8:15 pm

LMML it does have auto-thrust, the afterburners are operated by individual switches located at the base of the thrust levers, and as far as I'm aware the IRS is conventional.

Regards - Musang
 
CPH-R
Topic Author
Posts: 6164
Joined: Thu May 03, 2001 5:19 pm

RE: Concorde Eng #4

Tue Feb 19, 2002 10:22 pm

The reheats are primed, and once the throttle levers go beyond a certain position, they become engaged.
 
b767-400er
Posts: 384
Joined: Wed Apr 05, 2000 11:07 am

RE: Concorde Eng #4

Wed Feb 20, 2002 4:12 am

Confirm there are switches at the base of throttles for reheats, check this out:


Click for large version
Click here for full size photo!

Photo © Philippe noret



Those white switches are the reheat engage. Another interesting thing, when the Concorde is going transonic, the reheats are relighted 2 at a time because lighting them again at the same time would pin the pax against their seats for a second or 2.

Tony,
B767-400er
 
GDB
Posts: 13303
Joined: Wed May 23, 2001 6:25 pm

RE: Concorde Eng #4

Thu Feb 21, 2002 4:28 am

I was going to answer this one but Musang and B767-400er have done it for me!

 
CPH-R
Topic Author
Posts: 6164
Joined: Thu May 03, 2001 5:19 pm

RE: Concorde Eng #4

Thu Feb 21, 2002 7:29 am

Tony, then you can wonder if it would actually be a shame, or if it would add to the "glamour" of Concorde? I mean, which other passenger aircraft has the ability to pin you against the seat?  Big thumbs up
 
b767-400er
Posts: 384
Joined: Wed Apr 05, 2000 11:07 am

RE: Concorde Eng #4

Thu Feb 21, 2002 8:31 am

CPH-R:

Very true. But then, I guess people that can afford the 10 grands US (ie politicans, businessman, etc., perhaps a few rich avaition enthuasists) wouldn't want to be "shaken-up" a bit.  Smile/happy/getting dizzy Not to mention spilling their wines.  Laugh out loud

Tony,
B767-400er
 
CPH-R
Topic Author
Posts: 6164
Joined: Thu May 03, 2001 5:19 pm

RE: Concorde Eng #4

Thu Feb 21, 2002 9:10 am

Whoa, my bad. How could I forget the chadoonnay, champaign.. mmmhh... champaign...
 
GDB
Posts: 13303
Joined: Wed May 23, 2001 6:25 pm

RE: Concorde Eng #4

Sat Feb 23, 2002 3:16 am

You may be spared a kick in the pants when the reheats come on, but get ready for a fast stop when landing!
 
Trent_800
Posts: 136
Joined: Thu Jan 03, 2002 11:29 pm

RE: Concorde Eng #4

Sun Feb 24, 2002 7:35 am

Id be willing to bet most airliners (apart from A340  Wink/being sarcastic ) would pin you into your seat if it were traveling light and the pilot was having a bad day and firewalled the engines.
 
EssentialPowr
Posts: 1646
Joined: Wed Sep 06, 2000 10:30 pm

RE: Concorde Eng #4

Sun Feb 24, 2002 1:52 pm

CPH-R:
Differential thrust would cause a yaw, which would cause an uncoordinated turn.

Turning the Concorde is no different than turning a C172- it is accomplished by the horizontal component of lift as a result of a bank angle other than wings level.

Who is online

Users browsing this forum: United857 and 42 guests

Popular Searches On Airliners.net

Top Photos of Last:   24 Hours  •  48 Hours  •  7 Days  •  30 Days  •  180 Days  •  365 Days  •  All Time

Military Aircraft Every type from fighters to helicopters from air forces around the globe

Classic Airliners Props and jets from the good old days

Flight Decks Views from inside the cockpit

Aircraft Cabins Passenger cabin shots showing seat arrangements as well as cargo aircraft interior

Cargo Aircraft Pictures of great freighter aircraft

Government Aircraft Aircraft flying government officials

Helicopters Our large helicopter section. Both military and civil versions

Blimps / Airships Everything from the Goodyear blimp to the Zeppelin

Night Photos Beautiful shots taken while the sun is below the horizon

Accidents Accident, incident and crash related photos

Air to Air Photos taken by airborne photographers of airborne aircraft

Special Paint Schemes Aircraft painted in beautiful and original liveries

Airport Overviews Airport overviews from the air or ground

Tails and Winglets Tail and Winglet closeups with beautiful airline logos