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reverse before touch down

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reverse before touch down

Old 28th Feb 2019, 07:37
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reverse before touch down

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 :
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Old 28th Feb 2019, 07:39
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Certainly looks like it.

You can on the 737 too.
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Old 28th Feb 2019, 07:56
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Originally Posted by 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
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.
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Old 28th Feb 2019, 08:09
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You can on the 737 too.
Below 10 feet RA.
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Old 28th Feb 2019, 08:11
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Prohibited but possible below 10 ft RA on the 737 NG.
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Old 28th Feb 2019, 08:18
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plus Trident and TU-154 and IL62 iirc
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Old 28th Feb 2019, 11:39
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And Concorde.
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Old 28th Feb 2019, 11:44
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Originally Posted by Johnny F@rt Pants


Below 10 feet RA.
Every little helps!
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Old 28th Feb 2019, 12:50
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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 ?
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Old 28th Feb 2019, 13:08
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There was a thread about a while back on this.

737 Reverse before Touch?

Don't try it in a turboprop though.

https://en.m.wikipedia.org/wiki/Nort...nk_Flight_2268

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

Last edited by speedrestriction; 28th Feb 2019 at 13:19.
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Old 28th Feb 2019, 13:21
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Old 28th Feb 2019, 14:09
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Originally Posted by sonicbum
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.
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Old 28th Feb 2019, 14:34
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Originally Posted by EXDAC
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
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Old 28th Feb 2019, 14:37
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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.
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Old 28th Feb 2019, 14:47
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[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.

Last edited by EXDAC; 28th Feb 2019 at 15:42. Reason: deleted previous edit
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Old 28th Feb 2019, 15:24
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Could on the HS780.
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Old 28th Feb 2019, 15:58
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Originally Posted by EXDAC
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.
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Old 28th Feb 2019, 16:48
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Originally Posted by tdracer
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/...ts/AAR8116.pdf
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Old 28th Feb 2019, 17:49
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Also done by pilots on the 747s to land on short runways.
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Old 28th Feb 2019, 19:00
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Here is the 737 video:

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