reverse before touch down

[ATC Watcher]

I do not know how old this video is and apologies if it has been discussed before , but purely out of curiosity can you put reverse in flight on the MD80 . I know you could do it on the DC8 on the inboards to increase rate of descent , or even on all 4 on the CV990, but never heard it of newer types .
video here : MD80 reverse

[Chesty Morgan]

Certainly looks like it.

You can on the 737 too.

[sonicbum]

I do not know how old this video is and apologies if it has been discussed before , but purely out of curiosity can you put reverse in flight on the MD80 . I know you could do it on the DC8 on the inboards to increase rate of descent , or even on all 4 on the CV990, but never heard it of newer types .
video here : MD80 reverse (https://www.youtube.com/watch?v=3mzzt-tiUBk)

Hi,

in addition to the above, although I believe that on the MDs it is possibile to deploy the reverse at low radio alt, in this specific video You can see the aircraft experiencing a low bounce and then deploying the reversers.

[Johnny F@rt Pants]

You can on the 737 too.

Below 10 feet RA.

[ManaAdaSystem]

Prohibited but possible below 10 ft RA on the 737 NG.

[rog747]

plus Trident and TU-154 and IL62 iirc

[dixi188]

And Concorde.

[Chesty Morgan]

Below 10 feet RA.
Every little helps!

[ATC Watcher]

plus Trident and TU-154 and IL62 .... and Concorde
Thanks, did not know, if I may ask again , was that on all engines at all altitudes @ la Coronado or just above the runway to prevent a bounce as shown here ?

[speedrestriction]

There was a thread about a while back on this.

https://www.pprune.org/tech-log/516539-737-reverse-before-touch.html?highlight=reverse

Don't try it in a turboprop though.

https://en.m.wikipedia.org/wiki/Northwest_Airlink_Flight_2268

https://en.m.wikipedia.org/wiki/Luxair_Flight_9642

[Vessbot]

https://youtu.be/5gXfK4ypirI?t=23

[EXDAC]

Hi,

I believe that on the MDs it is possibile to deploy the reverse at low radio alt,



It's a very long time since I was involved with MD-80, but schematic 78-30-1 shows no RA input to reversers. I don't see anything on the schematic that would prevent reverser deployment in flight. Air/ground sensing is used to isolate the reverser accumulators from main hydraulics but does not seem to prevent deployment using the accumulators. My schematics date back to 1981 and there could have been changes since then so I'll defer to those with time on type.

[iggy]

I don't see anything on the schematic that would prevent reverser deployment in flight.

Haven't flown it for more than 10 years but I believe it was possible to deploy the reverses in flight. I never tried though :E

[twb3]

I was flight lead on an MD-80 series commercial airline trainer a long while ago. Unless there has been a mod since then, the reverser deployment command will not go true unless a main landing gear squat switch is made. In the video, the left main gear is seen to touch down briefly and the reversers deploy shortly after that. It appears to me that the reverser levers must have been in the reverse position, and the first bounce enabled the deployment. A lower order possibility is that one of the main landing gear squat switches was failed closed.

In any case, airborne deployment of the reversers is not a normal operation for the MD-80.

It is possible for the lower reverser bucket to strike the ground if the deployment sequence occurs with the main gear on the ground at higher pitch angles where the nose gear is not on the ground - adding code to detect this was the last change made before the trainer received FAA certification.

[EXDAC]

[QUOTE=twb3;10403017the reverser deployment command will not go true unless a main landing gear squat switch is made. [/QUOTE]

There is no "reverser deployment command" in the actual aircraft. The system is a mechanical linkage between the throttle quadrant and the reverser control valves.

[Squiffy Pussy]

Could on the HS780.

[tdracer]

There is no "reverser deployment command" in the actual aircraft. The system is a mechanical linkage between the throttle quadrant and the reverser control valves.

I don't know about the Douglas/MacDac aircraft, but Boeing put the air/ground on the hydraulic isolation valve (HIV), not the directional control valve on the cable engine aircraft.
The 737 uses radio altimeter for the air/ground because it has a tendency to float in ground effect and the squat switch doesn't activate - the others use the squat switch.

[EXDAC]

Boeing put the air/ground on the hydraulic isolation valve (HIV), .

On the MD-80 nose gear squat is used to isolate the reverser valve from main hydraulics but it leaves the reverser accumulators connected to the reverser valves. Having the main hydraulics isolated from the reverser valves by nose squat does not prevent reverser deployment. NTSB-AAR-81-16 illustrates what can happen if reversers are deployed before nose gear down. Note the procedure change that resulted from this flight test accident.

https://www.ntsb.gov/investigations/AccidentReports/Reports/AAR8116.pdf

[Ilyushin76]

Also done by pilots on the 747s to land on short runways.

[bumpy737]

Here is the 737 video:

https://youtu.be/-RO66a_nvus

[Smythe]

Wasnt that long ago when there werent reverse thruster locks...one could deploy them at any altitude.

then there is also this
https://youtu.be/mO-FdDKxuNU

[BluSdUp]

Smythe
That was SOP in ScotAirways in GLA in 1999. Even with a 90` turn.
Note to self: Do not use brakes to stop!
( Dornier 328 TurboProp)

[slack]

seen it done on dc8 43 series. Better be at altitude or real close to the ground or it could be nasty.

[WingNut60]

Smythe
That was SOP in ScotAirways in GLA in 1999. Even with a 90` turn.
........

And a wing mirror on a selfie stick?

[Atlas Shrugged]

Also done by pilots on the 747s to land on short runways.

Ummm... what?????

[vilas]

Also done by pilots on the 747s to land on short runways Not unless doing some shady work. Not at all recommended or required.

[Smythe]

There was a crash when a 767 deployed reverse thrust at 24,000...cant remember the year.

[sonicbum]

Is there seriously any professional pilot who advises on deploying thrusts reversers prior to touchdown ?

[ATC Watcher]

There was a crash when a 767 deployed reverse thrust at 24,000...cant remember the year.
Lauda air Bangkok 1991. But it was uncommanded on one engine only , the disymmetry caused the unrecoverable loss of control .

[bumpy737]

Is there seriously any professional pilot who advises on deploying thrusts reversers prior to touchdown ?

Well on the old IL-62 it was a part of the landing procedure as far as I remember :)

[Meikleour]

That was a standard technique that could be employed on DH Tridents - reverse in the flare - but that was 40+ years ago!

PS I do believe that the BEA/BA Trident pilots counted as professional pilots!

[HowardB]

Is it true that the RAF TriStars could apply reverse thrust before landing? Many year ago I was told that they competed to make the shortest landing at Stanley airport using revers thrust after the Falklands War

[DaveReidUK]

PS I do believe that the BEA/BA Trident pilots counted as professional pilots!

Ditto DC-8 pilots.

[CV880]

Back in the early 70's I saw a Swissair DC8-62 landing on runway 13 at Hong Kong Kai Tak with the reversers deploying well before touchdown (actually as it went passed the Aero Club which was where I was seated).. This was before the runway was lengthened and the aircraft looked a bit fast over the fence.
Also wasn't there an Alitalia DC8-62 written off at Sydney after a heavy landing because the pilot had selected reverse on the inboards in flight to expedite his descent and forgot about them until he tried to apply power on short finals?

[DaveReidUK]

Also wasn't there an Alitalia DC8-62 written off at Sydney after a heavy landing because the pilot had selected reverse on the inboards in flight to expedite his descent and forgot about them until he tried to apply power on short finals?

Yes, though it was at JFK rather than SYD.

https://twitter.com/aircrashmayday/status/851510199483584513

[tdracer]

No current production Boeing Commercial Aircraft allows the selection of reverse until the air/ground logic has been satisfied. In the case of the 737 the use of radio altimeter may mean you're not quite on the ground - but deploying them before actual touchdown is not approved and can be very hard on the aircraft (and perhaps your flying career). When the reversers deploy, the efflux kills the lift on that wing (as we discovered very unpleasantly on Lauda) and the aircraft drops like a rock. Plus, if one reverser fails to deploy for some reason you're also going to get a nasty roll at a bad time.

I'm with sonicbum. While it was possible (and even approved) on some older aircraft types, it's a very, very bad idea to try it on any current Boeing.

[etudiant]

No current production Boeing Commercial Aircraft allows the selection of reverse until the air/ground logic has been satisfied. In the case of the 737 the use of radio altimeter may mean you're not quite on the ground - but deploying them before actual touchdown is not approved and can be very hard on the aircraft (and perhaps your flying career). When the reversers deploy, the efflux kills the lift on that wing (as we discovered very unpleasantly on Lauda) and the aircraft drops like a rock. Plus, if one reverser fails to deploy for some reason you're also going to get a nasty roll at a bad time.

I'm with sonicbum. While it was possible (and even approved) on some older aircraft types, it's a very, very bad idea to try it on any current Boeing.

Was there not an Air Canada DC-8 that landed very hard due to early reverse thrust, was taken back up and crashed with all aboard lost? A very, very bad idea indeed for any civil transport.

[slack]

nope spoilers deployed prior to touchdown. big bounce, ripped off engine, opened wing and fuel caught fire. Game over crashed north of airport. cyyz All perished.

[andrasz]

Applying R/T on the outboards (only those had reversers) during flare was SOP on the IL-62. It had no leading edge slats, and was necessary to avoid floating in ground effect with the very efficient wing (for those times) at a high angle of attack. Mind you, originally it had a five person fight deck...
Good video here: https://www.youtube.com/watch?v=eYuiWPoIbew

[Ilyushin76]

Is there seriously any professional pilot who advises on deploying thrusts reversers prior to touchdown ?

Yes, I can name a few. All pilots of classic aircraft such as the 707/A300/747 combis..

[fdr]

Ummm... what?????

I second the, Ummm... what????

Where is that written in ANY Boeing, Airbus, Embraer FCTM or OM????

A disproportionate number of pod scrapes were caused by the stupidity of crew placing their hands on the TR levers and lifting one immediately on touchdown, where a bounce or skip resulted. Make no mistake, if I am a passenger in an aircraft and see a TR deploy on any Jet airborne, the regulator will get all the information that I can put together. As a training point, IN THE SIMULATOR, if someone puts their hands on the TR's in the flare, I called GA. If they did it in an aircraft while I was doing standards, they got another evaluation ride. If you do it on any of my jets, I will get your hands off the levers. It is unconscionable to risk the aircraft just because the pilot doesn't know where to put his damned hands. If you need to recklessly endanger yourself by landing on a runway that is so short that you are compelled to do a non standard procedure, then you have already made a bad decision. No OEM recommends immediate TR on touchdown, before the aircraft is fully ground bound. Forgetting the spoilers will get you into serious problems in this event.

WTF!

Back in the military we used to pull reverse in the air, work fine if it is symmetrical and everything else works correctly. Any error and people die. People did die doing that.

FYI, the cause was slightly different, but this is the sort of outcome that lies in wait of having one engine in full thrust (for a dart that is a relative term) and one that is not, at low speed. If you think it is fine to grab early reverse, just tell the passengers what your VMCair or VMCground is for having one engine in reverse (even at idle) and the other at GA thrust.

https://cimg8.ibsrv.net/gimg/pprune.org-vbulletin/1000x505/xs609_1_b6181949e96586e6bf58f7c31d4953236e8cd9d4.jpg

[OK4Wire]

Not to mention all versions of the Harrier/Sea Harrier! :O

[MetoPower]

DC8-60 Series: inboard reversers available in flight with gear handle in up position, but restricted to reverse power stop. All 4 engines with gear handle in down position. I think the older series where similar.
Trident: reversers on engines 1 & 3 available in flight – the descent rate was in rather interesting to say the least. Reverse thrust was indeed selected just before touch down (below 50 ft RA).

MP

[sonicbum]

I second the, Ummm... what????

Where is that written in ANY Boeing, Airbus, Embraer FCTM or OM????

A disproportionate number of pod scrapes were caused by the stupidity of crew placing their hands on the TR levers and lifting one immediately on touchdown, where a bounce or skip resulted. Make no mistake, if I am a passenger in an aircraft and see a TR deploy on any Jet airborne, the regulator will get all the information that I can put together. As a training point, IN THE SIMULATOR, if someone puts their hands on the TR's in the flare, I called GA. If they did it in an aircraft while I was doing standards, they got another evaluation ride. If you do it on any of my jets, I will get your hands off the levers. It is unconscionable to risk the aircraft just because the pilot doesn't know where to put his damned hands. If you need to recklessly endanger yourself by landing on a runway that is so short that you are compelled to do a non standard procedure, then you have already made a bad decision. No OEM recommends immediate TR on touchdown, before the aircraft is fully ground bound. Forgetting the spoilers will get you into serious problems in this event.

WTF!

Back in the military we used to pull reverse in the air, work fine if it is symmetrical and everything else works correctly. Any error and people die. People did die doing that.

FYI, the cause was slightly different, but this is the sort of outcome that lies in wait of having one engine in full thrust (for a dart that is a relative term) and one that is not, at low speed. If you think it is fine to grab early reverse, just tell the passengers what your VMCair or VMCground is for having one engine in reverse (even at idle) and the other at GA thrust.

https://cimg8.ibsrv.net/gimg/pprune.org-vbulletin/1000x505/xs609_1_b6181949e96586e6bf58f7c31d4953236e8cd9d4.jpg

excellent post.

[vilas]

Yes, I can name a few. All pilots of classic aircraft such as the 707/A300/747 combis.. Definitely not on those aircraft unless they are Kamikaze pilots making their own procedures.

[VinRouge]

Boeing C-17 does it no problem. Great fun too. Rod tops out at 20kft/min on the way down and is fully cleared by manufacturer.

[tdracer]

Boeing C-17 does it no problem. Great fun too. Rod tops out at 20kft/min on the way down and is fully cleared by manufacturer.

Also not certified Part 25...
Military aircraft are allowed to do many things that are not allowed under Part 25.

[Uplinker]

Airbus A320 family have a useful partial ground spoiler mode where if one main landing gear has weight on wheels, selecting idle reverse will give you 10 deg spoiler deployment to reduce wing lift and ease the aircraft down. (As long as the spoilers were armed before landing, which is SOP anyway).

[VinRouge]

Also not certified Part 25...
Military aircraft are allowed to do many things that are not allowed under Part 25.

Does part 25/cs25 prohibit in flight reverse? Or is it not more of, it’s not a requirement of civilian jets to drop 20k/min and therefore an unnecessary feature?

[tdracer]

Does part 25/cs25 prohibit in flight reverse? Or is it not more of, it’s not a requirement of civilian jets to drop 20k/min and therefore an unnecessary feature?


No, in-flight reverse is not specifically prohibited. However, everything needs to comply with 25.1309 - which in short means that the probability of a catastrophic event has to be less than 1 in a billion (per flight hour) and that no single failure can have a catastrophic outcome (i.e. you can't use probability arguments for single failures, structural elements excluded).
Now, look at what happened on Lauda - the reverser deployed on one side (uncommanded) - the resultant upset caused complete loss of control in a few seconds and aircraft breakup shortly there after. In order to certify in-flight reverse use, you'd have to definitively show that Lauda couldn't happen if you got unsymmetrical reverse deployment.
I very seriously doubt you could get there (and I sure as hell wouldn't want to be on a flight test to try it).
Beside, yes, it's an unnecessary feature. Passenger O2 requirements assume an idle descent from the max certified altitude - no need to get down even quicker than that. And in the extraordinary event that you do need to come down faster than idle with speed brakes, you're best bet is to drop the landing gear - it may cause damage to the gear doors, but it's readily controllable.

[AviatorDave]

...reverse thruster...

omg. You a pilot?

[VinRouge]

No, in-flight reverse is not specifically prohibited. However, everything needs to comply with 25.1309 - which in short means that the probability of a catastrophic event has to be less than 1 in a billion (per flight hour) and that no single failure can have a catastrophic outcome (i.e. you can't use probability arguments for single failures, structural elements excluded).
Now, look at what happened on Lauda - the reverser deployed on one side (uncommanded) - the resultant upset caused complete loss of control in a few seconds and aircraft breakup shortly there after. In order to certify in-flight reverse use, you'd have to definitively show that Lauda couldn't happen if you got unsymmetrical reverse deployment.
I very seriously doubt you could get there (and I sure as hell wouldn't want to be on a flight test to try it).
Beside, yes, it's an unnecessary feature. Passenger O2 requirements assume an idle descent from the max certified altitude - no need to get down even quicker than that. And in the extraordinary event that you do need to come down faster than idle with speed brakes, you're best bet is to drop the landing gear - it may cause damage to the gear doors, but it's readily controllable.


So on the C17, im fairly sure a similar probability loss model is used. If 2 of 3 interlock prox sensors indicate TR deployment in flight (or if 2 prox sensors fail in flight and loose resilience), the controller automatically commands flight idle on that engine. So its not impossible (nor difficult) to meet FAR/CS25 requirements in a modern aircraft design if this design were adopted. But again, structure would need to be beefed up (weight cost, complexity etc), and there is no role requirement for it, hence why its not a design feature.

If I were in a similar scenario in a commercial equivalent (Lauda scenario) the T-Handle would be the best place to start I suspect. But that would require very rapid actions and realization of what is happening pretty quickly.

[bafanguy]

If I were in a similar scenario in a commercial equivalent (Lauda scenario) the T-Handle would be the best place to start I suspect. But that would require very rapid actions and realization of what is happening pretty quickly.

VinRouge,

Precisely. There was a case in KATL where an Eastern DC9 was dispatched with a thrust reverser inop which required MTC to perform some actions back near the engine to isolate the reverse mechanism from hydraulics (the details of that escape me at the moment). This had to have been in the late 1970s, early 1980s.

Well, the MTC action wasn't done correctly and the inop reverser came open at rotation on takeoff. The crew overcame the surprise and got the airplane into the air and back on the ground. It was a real feat of airmanship.

We tried it in the sim and found the only way to not lose control of the airplane was to snap the throttle to idle and shut off the fuel. It was still a handful even when we knew it was coming.

Those EAL guys really did a great job. I tried to find an article about it but couldn't.





i

[jimtx]

VinRouge,

Precisely. There was a case in KATL where an Eastern DC9 was dispatched with a thrust reverser inop which required MTC to perform some actions back near the engine to isolate the reverse mechanism from hydraulics (the details of that escape me at the moment). This had to have been in the late 1970s, early 1980s.

Well, the MTC action wasn't done correctly and the inop reverser came open at rotation on takeoff. The crew overcame the surprise and got the airplane into the air and back on the ground. It was a real feat of airmanship.

We tried it in the sim and found the only way to not lose control of the airplane was to snap the throttle to idle and shut off the fuel. It was still a handful even when we knew it was coming.

Those EAL guys really did a great job. I tried to find an article about it but couldn't.





i
They did. I don’t remember if it was ATL or TPA. We then practiced it in the sim. But “barborpole”, EAL Capt on the 727-100, always popped the reversers in the flare at STX. Worked great. I did it once floating at DCA in a 200. Worked great. Not recommending it anymore.

[tdracer]

So on the C17, im fairly sure a similar probability loss model is used. If 2 of 3 interlock prox sensors indicate TR deployment in flight (or if 2 prox sensors fail in flight and loose resilience), the controller automatically commands flight idle on that engine. So its not impossible (nor difficult) to meet FAR/CS25 requirements in a modern aircraft design if this design were adopted. But again, structure would need to be beefed up (weight cost, complexity etc), and there is no role requirement for it, hence why its not a design feature.

If I were in a similar scenario in a commercial equivalent (Lauda scenario) the T-Handle would be the best place to start I suspect. But that would require very rapid actions and realization of what is happening pretty quickly.

The devil is in the details. When the T/R deployed on Lauda, the FADEC immediately commanded idle thrust on that engine (as is required by the regulations). But big turbine engines don't respond immediately - it takes finite time to spool down - especially at altitude - and by the time the event engine got close to idle, it was already too late - the aircraft was out of control and already coming apart (I was directly involved in the Lauda investigation - it wasn't pretty). If an engine is significantly above idle with asymmetric reverser deployment, you're F:mad:ed. Simply failing to wait until the engine spooled down to idle before commanding in-flight reverse could be catastrophic with asymmetric reverse at altitude.
With the old pure jet and low bypass engines, in-flight reverse - even if something went wrong - wasn't a big deal. But what we didn't know before Lauda was that with high bypass engines it's a whole different story (and the F117 - aka PW2000 - is most definitely a high bypass engine). Had the C-17 been Part 25 certified, in-flight reverse would have been banned in the aftermath of Lauda.
The Lauda crew knew that something funny was going on with the reverser before the deployment occurred - but still were unable to perform a shutdown of the engine in time to prevent complete loss of control. and the resultant aircraft breakup.
Boeing looked at doing a Part 25 cert of the C-17 (abandoned due to insufficient interest to justify the costs). In flight reverse would have been among the first things to get deleted.

Edited to add - the C-17 was designed and put into production pre-Lauda. They hadn't yet learned the Lauda lesson of what high bypass reverse in-flight can do. The analysis that the 767/PW4000 reverser was safe - even with an in-flight deployment - was done as part of the certification. Problem was it was WRONG.
We know better now.

[DaveReidUK]

They did. I don’t remember if it was ATL or TPA.

Hartsfield, April 1985. The T/R control valve handle had been installed incorrectly.