Reverse thrust in flight

[KLOS]

I wa reading the background to the LAUDA B767 accident and I understand that when investigators tried ehe scenarion in the sim ,they discovered after some trials, that an aircraft was theoretically recoverable but in a very small time window ( 4-6 secs?) provided that the pilots were aware of that which needed to be effected. Can any professional confirm whether pilots are required to practice such a scenario in the sim or is it that the subsequent inhibit technology now guarantees (?) that such a scenario is not posible thereby rendering such scenario not requisite training . I think it ia analogous to the rudder hard -over on B737s raising the same questions- grateful for any advice from the Pros. Thanks

[Dave Barnshaw]

As far as I understand,the only aircraft to successfully apply reverse thrust in flight was Concorde,and that was used to slow the aircraft back down to subsonic speeds.:=

[BOAC]

Yes it is practised in the sim. The 'crippler' is an aircraft with 'bucket' reversers, and you need to be quick to identify and shut down particularly on take-off.

[exeng]

As far as I understand,the only aircraft to successfully apply reverse thrust in flight was Concorde,and that was used to slow the aircraft back down to subsonic speeds.

Where are all the ex Trident Pilots when you need them!


Regards
Exeng

[BOAC]

that was used to slow the aircraft back down to subsonic speeds. - I doff my hat to those guys:rolleyes: - deploying a reverser or two at Mach 2 - wow! Cojones of steel, eh. (the late, lovely Barbara excluded, of course)

[dixi188]

DC-8 with stove pipe engines was allowed to reverse inboards in flight. Not allowed on the CFM56 powered ones though.

[Juliet Sierra Papa]

I think the Il-62 inboards allowed this. Did the VC-10 operate this way?

[Denti]

Well, barely inflight but on the 737 you can open reverse below 10ft radar altitude. It is not recommended of course, but possible.

Apart from a demonstration during initial type rating we never trained an open reverser inflight, reverser unlock light yes, but not actually opened.

[Tu.114]

On the F70/100, it was occasionally trained in the simulator.

The engineers at Fokker were smart guys - they installed a cable between the reverser buckets and the fuel control unit that forces the thrust levers to idle (and slammed the lever to that position quite forcefully) whenever the buckets were opened. Any desired reverse thrust increase had to be commanded via the TR levers only.

It certainly was a bumpy experience until the engine was shut down, but I was under the impression that it was flyable. However, I have no desire to try this in a real plane.

[paulsalem]

C-17 Can do it on all 4 engines. Rates of descent can exceed 15,000fpm

[The SSK]

I've experienced it as a passenger in a Trident landing on a snow-covered runway at Newcastle. Roar, Thump.

[Desert185]

dixi188:
DC-8 with stove pipe engines was allowed to reverse inboards in flight. Not allowed on the CFM56 powered ones though.

While discouraged for structural and passenger comfort reasons, reverse inflight IS allowed on CFM56 powered DC-8's, just as the earlier powered ones. Inboards only (the outboards are locked out with the gear up). Inflight reverse stops limit amount of reverse, and stowing should be with an IAS of less than 300kts. Very effective, and will peg the 6,000fpm VSI during an emergency descent.

The Emergency Stow Pump still exists, as it did prior to the CFM engine mod.

The spoiler system is only for roll control assist with the gear down and for spoiler deployment after touchdown. No speedbrake duties.

[BN2A]

Concorde didn't decellerate with reverse, it was an option (with various do's/don'ts/be carefuls) to increase rate of descent..

Have seen an uncommanded thrust reverser deployment on the 757 just after take off (in the simulator...), and neither training captain could recover it!!

:uhoh:

[matkat]

Agreed the CFM powered DC8s were indeed authorised for in-flight reverser deployment, experienced it many times working as a flight tech on board Southern air transports DC8s.

[flying officer kite]

Concorde, the Tridents, the Caravelle, the NASA 'shuttle-trainer' gulfstreams, and the Tu154 could all use reverse thrust in flight

[dixi188]

I stand corrected re. the CFM powered DC-8.

I was jumpseating on a UPS DC-8-73 some years ago when the capt. pulled the inboard reverse levers in descent. The Flight Engineer slapped his hand down and said "No you don't, not with these engines"

Maybe it was a UPS thing or just bad CRM.

[777fly]

OK, I've waited long enough, an ex Trident pilot has to give an input at some time in this thread......

The Trident might not have leapt skywards, as is the current fashion, but it was certainly a high speed cruiser, Mno 0.885 for the Trident 1A, if I remember correctly. However, the use of in flight reverse made it capable of rates of descent similar to that of a falling manhole cover. With the speed pegged at cruise Mach, transitting to 380 kts Vmo, full speed brake, plus about 90% reverse thrust on the pod engines it was capable of rates of descent in excess of 18,000 ft min. ATC were aware of this re-entry capability and often made good use of it.
Furthermore, to improve stopping capability on short runways, full reverse could be selected in the landing flare so that max reverse thrust was being achieved at touchdown. There was a natural pitch up with this technique which usually helped smooth the touchdown, but the slightest misjudgment could result in in very firm touchdown.

I would be interested to know if other types with in-flight reverse were allowed to use more than reverse idle power.

[KLOS]

Many thanks for all your responses

[bingofuel]

it was capable of rates of descent in excess of 18,000 ft min.

I bet the engineer had fun getting the cabin to stay ahead in the descent!

[777fly]

Bingofuel:

I detect a note of scepticism methinks.
18,000fpm is a genuine figure and could be exceeded. It was achievable at higher levels but it was only too easy to 'catch the cabin' if those descent rates were sustained to low altitude. There was a 'bird speed' restriction at lower altitudes and the manoeuvre required to back the speed off by 70kts or so usually gave the cabin time to get back on schedule. It did need careful watching, but by a third pilot on the systems panel, not a F/E.
By the way, the Trident model I describe was a 1C, drooped leading edge and 38 degree sweepback.

[KLOS]

Would a Pro kindly explain the procedure for recovering from an uncommanded reverse thrust in the cruise.

Many thanks

[Rollingthunder]

Was on a DC8-63 coming back from Fiji (mostly snorkeling). Diving, caught a cold, kept diving. DC8 popped the inboards on arrival at YVR. Dropped like a stone. Nothing wrong with a/c but something was wrong with me. On the ground was totally deaf. Going through customs was interesting to say the least. When it hadn't cleared up a week later I went in for sinus surgery to fix the problem. Spent the next couple of weeks with cotton wool shoved up my nostrils.

[BOAC]

Would a Pro kindly explain the procedure for recovering from an uncommanded reverse thrust in the cruise. - follow the QRH which normally ends with 'shut down the motor' if all else fails.

[Desert185]

dixi188:I was jumpseating on a UPS DC-8-73 some years ago when the capt. pulled the inboard reverse levers in descent. The Flight Engineer slapped his hand down and said "No you don't, not with these engines"

Maybe it was a UPS thing or just bad CRM.

UPS preferred that reversers not be used inflight unless for an emergency descent or for some other operational reason based on the Captain's judgment. It seems the FE may have acted inappropriately, even though he may have been right. :=

[Desert185]

klos:
Would a Pro kindly explain the procedure for recovering from an uncommanded reverse thrust in the cruise.

Many thanks

Depends on the aircraft.

DC-8: Reverse Thrust Lever - FORWARD IDLE; Emergency Stow Pump - ON; If reverser fails to stow: Engine - SHUTDOWN

Other aircraft without an emergency stow pump: Thrust Lever - IDLE; If the reverser doesn't stow - Engine - SHUTDOWN

Essentially, select idle power and hope it stows. If not, engine shutdown is necessary to reduce asymmetry. Most airplanes these days don't have buckets that reverse core air. Only the fan air is reversed, so the drag increase and asymmetry is less.

[KLOS]

Thanks BOAC and Desert 185 for your replies.

My ( lay) reading of the LAUDA B767 accident report was that the effect was to invert the aircraft resultng in its destruction by excessive G when recovery was attempted. As I recall the pilots were seeking to consult the manaual for guidance. Also as I mentioned originally , I understood that the sim reconsruction indicated a small window of circa 6 seconds for recovery . Have I got this right? - grateful for any further comment from the Pros.

Thanks

[BOAC]

The effect of a deployed reverser at high power (I think Lauda were climbing) is dramatic. A combination of loss of forward thrust, asymmetric couple and loss of lift from the disturbed airflow mean the rolling moment is huge, and 6 seconds may well be right. If action is not taken quickly extreme bank angles can develop.

It is also quite dramatic during take-off, especially with bucket type reversers since all engine-out performance calculations are negated. We have a thread somewhere about that.

[KLOS]

BOAC

Many thanks for this very informative response.