rb211
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What With Thrust Reverse Prior To Touchdown.

Thu Oct 30, 2003 12:54 am

Why do some airlines perform thrust reversal prior to touch down. I've seen several Russian aircraft perform it but have yet to see any European or American aircraft do it. Wouldn't that stress the landing gear when it hits the tarmac?
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avioniker
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RE: What With Thrust Reverse Prior To Touchdown.

Thu Oct 30, 2003 2:04 am

The only US built aircraft I know that can reverse in flight (without pulling certain breakers that shouldn't be pulled in flight) is the DC-8 and that's because it's really slick and that's the only way to make some of the approach points on speed.
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JBirdAV8r
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RE: What With Thrust Reverse Prior To Touchdown.

Thu Oct 30, 2003 2:14 am

To elaborate on what Avioniker said, it's also because the aircraft has no flight spoilers (only ground spoilers), and isn't it only the inboard engines that can be reversed in flight?

Also NASA's modified Gulfstream II Shuttle Training Aircraft can reverse in-flight; they are modified with different (727-style) reversers.
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RE: Bad Image By The Crew

Thu Oct 30, 2003 2:15 am

The DC8 can use inboard engine reversers (Douglas name is "thrust brakes") in flight. The DC8 could not use their spoilers in flight... so like Avioniker said, the only way to slow down a DC8... is deploy inboard reversers...
xxx
The DC8 had a very low speed limit for flaps and gear extension (230 KIAS for both)... so when you were at say... 250, descending to intercept a glide slope and still no slowing down, especially with these CFM engines, the only way to slow down was the reversers... until you hit 230, then get the flaps...
xxx
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USAFHummer
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RE: What With Thrust Reverse Prior To Touchdown.

Thu Oct 30, 2003 2:46 am

Alas, to add a little bit on to JBird, the NASA Gulfstream is flown in a fashion that should not be attempted by a normal Gulfstream with steep dives at high speeds, hence the need for the reversers inflight...its like "do not try this at home kids"...

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broke
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RE: What With Thrust Reverse Prior To Touchdown.

Thu Oct 30, 2003 2:53 am

The DC-8 is certified to use its inboard thrust reversers in flight, but using it inflight really reduces flap reliability due to the buffeting they receive. The -70's series with the high bypass engines aggravates the problem even more.

I have seem IL-62's on short final with the thrust reverser buckets on the outboard engines deployed. I think that the outboard engines are the only ones on the IL-62 with thrust reversers. I don't know the reason for deploying the buckets in flight. My guesses run from using them as a speed brake or slow deployment of the reversers on the ground.

Does anyone know for a fact why??
 
lehpron
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RE: What With Thrust Reverse Prior To Touchdown.

Thu Oct 30, 2003 2:09 pm

Doesn't reversing inflight risk a backflow up the tailpipe?
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scbriml
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RE: What With Thrust Reverse Prior To Touchdown.

Thu Oct 30, 2003 3:54 pm

I have seem IL-62's on short final with the thrust reverser buckets on the outboard engines deployed

You mean like this:
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POSITIVE RATE
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RE: What With Thrust Reverse Prior To Touchdown.

Thu Oct 30, 2003 3:56 pm

I recall reading somewhere Concorde could deploy reversers in flight too.
 
A/c train
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RE: What With Thrust Reverse Prior To Touchdown.

Thu Oct 30, 2003 4:57 pm

It depends on the systm design aswell as crew demands, on some a/c, it needs air/grnd sensing for example, on older a/c a microswitch/proximity sensing on the undercarriage leg deployed speed brakes and reversers.
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LZ-TLT
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RE: What With Thrust Reverse Prior To Touchdown.

Thu Oct 30, 2003 11:05 pm

On the Il-62M, it is a standart procedure to use reversers prior to touchdown, and the 62 IS equipped with speedbrakes/spoilers. On both 62 design variants(62/62M the outboard engines are the only ones equipped with reversers). I think, it has to do with the slow spool-up rate and high idle trust on these engine types - the Kuznetzov NK-8-2 on the original Il-62 and the Solovjev D-30KU on the 62M. Also, the original 62 is equipped with cascade-type reversers while the (much more popular) 62M has the clamshells as shown on the photo
 
rb211
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RE: What With Thrust Reverse Prior To Touchdown.

Fri Oct 31, 2003 12:25 am

That's what I was talking about (the picture)Scbriml. Hey guys thanks for clearing that up. I just looks really crazy.
Thanks lots!

P.S. "The next station is concourse E. Concourse E is your next station!"
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sovietjet
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RE: What With Thrust Reverse Prior To Touchdown.

Fri Oct 31, 2003 1:37 am

Then why don't the Tu-154s do what the Il-62s do? Tu-154s have the exact same engines(Tu-154A/B is NK-8-2 and Tu-154M is D30KU). Yet I have never seen one do that not even a picture. Why would only the Il-62 do it? Il-76 same story....
 
fritzi
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RE: What With Thrust Reverse Prior To Touchdown.

Fri Oct 31, 2003 3:47 am

Concorde can use the reversers inflight, but only on the Inboard reversers (i think) and with the engines running at idle thrust.
 
justplanesmart
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RE: What With Thrust Reverse Prior To Touchdown.

Fri Oct 31, 2003 7:25 pm

Sovietjet:


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sovietjet
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RE: What With Thrust Reverse Prior To Touchdown.

Sat Nov 01, 2003 1:28 am

Wow first time I've seen that. And all the summers in Sofia not one Tu-154 did that. Maybe they don't do it as often on -154s.
 
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Francoflier
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RE: What With Thrust Reverse Prior To Touchdown.

Sat Nov 01, 2003 11:41 am

In the Yak-40, it is standard procedure to reverse the #2 engine about 30 ft above the ground just before the flare.

It is the only engine that's "reversible" on this a/c (the tail mounted one).

The yak-40 is a funny aircraft. It looks like it is powered by three APUs (only 5000lbs of thrust each or so) and has a landing gear that makes it look like it's able to land where a humvee couldn't go...
It also leaves a nice environment friendly black trail wherever it goes, let alone the noise.

I like russian jets, they're workhorses...
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LZ-TLT
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RE: What With Thrust Reverse Prior To Touchdown.

Sat Nov 01, 2003 10:19 pm

Sovietjet,

Assuming, you're from Bulgaria, which version of the 154 did you see at LBSF? Balkan had both the B2 and the M series. On the B2, they have cascade-type reversers, so it is not that easy to tell if they are engaged. Also, power to weight ratio might be a factor here. The Tu-154 is(let's face it), somehow poorly designed with an overweight airframe, and this is compensated by the extensive wing mechanization(Kruger leading edge flaps, tripple-slotted Fowler trailing edge flaps, etc). The Ilyushin and Yakovlev designs are not so heavy and much more optimized. So, where you can slow a Tu-154 down by using the flaps and speedbrakes, an Il or Yak keeps on going. Flaps are not that much of an option, taking into account that Flaps 45 degrees on the Tu-154(the usual landing configuration) produce more extra drag than lift, something what the simpler flaps(two-section-single-slotted flaps on the Il-62) can't accomplish
 
sovietjet
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RE: What With Thrust Reverse Prior To Touchdown.

Sun Nov 02, 2003 5:34 am

LZ-TLT,

Are you Bulgarian too? I would assume so because LZ- is on all Bulgarian aircraft. Kade jiveesh? Anyway yea I know the B2 has cascade reversers but you could possibly tell from the noise if it's in reverse or not. I should rephrase and say that I've never seen a Tu-154M use reverse in Sofia.
 
LZ-TLT
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RE: What With Thrust Reverse Prior To Touchdown.

Sat Nov 08, 2003 8:43 pm

Sovietjet,

Yes, I am Bulgarian, living in Germany by now(left Bulgaria 5 years ago, but still go down there for my summer vacation)

As for the reversers of the Il-62 and the Tu-154: last night i talked with a former 154 Pilot and he was able to explain to me the whole thing:

deploying the reverser vanes does not actually mean putting the plane into reverse per se. Depending on weight of the aircraft, approach speed, runway length and conditions, the reverser vanes or buckets are deployed in the final phase of the landing prior to touchdown, but the engines are kept idling(or one can even add thrust using the inboard engines on the Il-62/62M and the middle(Nr2) engine on the Tu-154. The effective reverse thrust is obtained AFTER touchdown by spooling the engines up and is regulated smoothly by the throttle(on the Il-62, it is allowed to spool up the engines to 60% of the takeoff thrust when in reverse). The whole thing is also a complicated procedure requiring fine-tuned crew ressource management. The guy who I talked was also able to describe it in detail.
 
wannabe
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RE: What With Thrust Reverse Prior To Touchdown.

Sun Nov 09, 2003 4:27 am

How does that effect your ability to execute a last minute missed approach or go around? I would imagine you have to lose a few seconds while the reverser is "re-stowed".
 
TheGov
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RE: What With Thrust Reverse Prior To Touchdown.

Sun Nov 09, 2003 9:43 am

I am not a pilot nor an employee of Fed Ex, but I recall reading somewhere that Fed Ex was, at one time, using reverse thrust in-flight on its B-727s. The article stated that Fed Ex was experiencing higher than normal wear on its engines due to this practice and was going to stop in an effort to reduce expenses as well as the mentioned wear and tear. Why was it done? According to the article, Fed Ex was flying higher and faster closer to the airport in an effort to reduce block times and was using in-flight reverse thrust to slow down on approach.

Unfortunately, I am relying on my memory. I think this article appeared about 5-7 years ago. I had assumed, until the article appeared, that in-flight thrust reverse was dangerous (a la Lauda B-767 crash) and was surprised to hear that it was common practice.

Like I said, I am not a pilot, an employee of Fed Ex and an relying solely on memory.
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