Jean Leloup
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What Is Sticking Out The Back Of This RJ85?

Tue May 01, 2001 1:36 pm

I'm sure all you guys know this, but I've never noticed it before. AS you can see it comes out from the rear starbord side.. I guess there's one on the other side too. Is it some kind of brake that pops out?

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Tue May 01, 2001 1:39 pm

Yes, that is an airbrake. It is used on final approach and landing to.. slow the plane. Avro RJ's don't have thrust reversers, and this acts as a replacement of sorts.


By the way, yes there is also one on the port side.
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RE: What Is Sticking Out The Back Of This RJ85?

Tue May 01, 2001 1:51 pm

You'll also see the same kind of thing on the Fokker F28! The airbrake opens and closes like a clamshell.
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RE: What Is Sticking Out The Back Of This RJ85?

Tue May 01, 2001 5:27 pm

Yes indeed, it's an airbrake, and it consists of 2 parts, one on the port side , and one on the starboard side. These two parts open up, in order to slow the aircraft down. The opening takes only 2 seconds or so.

From what I've seen so far at EBBR (Brussels), pilots landing the RJ usually open up this airbrake only a few moments before touching down. Some pilots only deploy them just after touching down. It all depends on the approach I guess.

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RE: What Is Sticking Out The Back Of This RJ85?

Tue May 01, 2001 7:17 pm

Yeah it often depends where the pilot deploys them. I live in Detroit, Northwest/Mesaba fly a ton of them into their Detroit hub and I have noticed that some aren't deployed until they are practically on the ground while some others deploy them several thousand feet up before they even circle in to land over my house which is about 20 miles away from the airport and not in the landing pattern of DTW.

Most of them do their turns around my house though.

Since we are on the subject of RJ85s, what is that strange noise that they make when they circle in to land??? It is something that they do with their engine like changing power or something that makes the strangest eeriest groaning sound.
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Tue May 01, 2001 7:35 pm

It's true that some Avro RJ pilots open the rear speedbrake long before touching down and some only after. The Avro RJ has also speedbrakes on the wings that are mostly opened after touchdown.
I flew on one of those two weeks ago. I sat behind the engines and it was awfully loud. I noticed that the exhaust of the inboard engines hit the flaps if they're fully deployed. When the engines spool up the flaps start to vibrate and the sound is incredible. It's the same when landing. Maybe the sound you're hearing is when the flaps finally heat the airflow of the engine.
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RE: Fokker 28, 100 And 70 Had Them Too!

Tue May 01, 2001 8:10 pm

Air brakes!
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RE: What Is Sticking Out The Back Of This RJ85?

Tue May 01, 2001 9:57 pm

Hey, Blackend, perhaps you can advise me. What row did you sit in? I'd like to sit behid the wings and engines too. Thansk for any advice.
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RE: What Is Sticking Out The Back Of This RJ85?

Wed May 02, 2001 4:06 am

On the RJ/RJX/146, the airbrakes are the clamshell doors at the rear fuselage. They can be used at any speed. The lift spoilers are for ground use only and are on the top surface of the wings immediately ahead of the flaps. They are deployed automatically on touchdown on the RJ/RJX. The hooting noise is generated when the flaps are deployed from up to the 18deg position and is caused by reverse flow under the wing. It is not dependent on engine RPM but does vary with the speed at which the flaps are deployed. In the landing position the flaps do come close to the jet efflux. If you want a quiet ride I would sit near the front. Also at the back you get the hot jet efflux distorting the air behind the exhaust nozzles.

Hope this clears up a few points.


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RE: What Is Sticking Out The Back Of This RJ85?

Wed May 02, 2001 4:06 am

Isn't it awful the sound of the flaps extending? It is even audible from the ground. It is unmistakeable. Like a train coming to a stop at an underground station. The sound was even detected by the DB noise meter during trials ! And yes I noticed the flaps vibrating too. The RJ's with LF505 engines have a lot of problems with them. When Airmalta used to operate four RJ70's we used to have an average of one engine write off a month.
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RE: What Is Sticking Out The Back Of This RJ85?

Wed May 02, 2001 4:38 am

By the way, one very interesting beneficial side effect of the rear-mounted split airbrake is that they mitigate the effects of a nasty aerodynamic effect called deep stall, where the horizontal stabilizers on a T-tail airplane lose effectiveness at certain angles of attack and the plane literally can fall out of the sky.

Indeed, when Fokker introduced them on the F28 Friendship, it allowed the plane to have much more benelovent stall regimes.
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Wed May 02, 2001 11:37 pm

I sat in the 2nd last row on a Crossair flight from ZRH to BSL. It was a 20 minutes flight so the sound was no problem. Might be worse on a longer flight. You can really hear it when the flaps are deployed. It's about twice as loud.
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