I was reading the accident report of flight JA 8032 which water-landed in SFO bay (1968), and I found this:

"... In-flight reversing of the two inboard engines was utilized to insure than descend to the 8000 ft level wold be accomplished in time to conform with the ATC clearance..."

Is this a normal procedure?
Is this done only with 4 engined-planes?

As far as i know only the DC-8 could use reverse during descent and only on the 2 inboard engines.... was this JA 8032 flight a DC-8?
I don't know about any other plane nor if it was common or not...

On todays quads (B747/A340/BA146) it certainly is NOT practiced, in fact it is made impossible!

In the Il-62 is also possible to deploy inboard thrust reversers in flight


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Photo © Andreas Heilmann

Il-62s only have outboard reversers. Tu-154 can use reverse thrust in flight also.

Among the various types it may, or may not be permitted. I'm not sure whether there are any types that have reverse locked out in flight or not. IIRC it was a high-drag option for the DC-8 to reverse two engines inflight.

In any aircraft the manual should be consulted. Consequences might range from nothing more than noise and vibration all the way to disaster.

Yes the JAL landing in SFO bay was a DC-8. See some older threads about water landings for more details.

The DC-8 does not have flight spoilers, so the inboard thrust reversers can be used in flight to slow the airplane down and descend rapidly.
Unfortunately, the bad part is that the turbulent airflow causes a lot of wear and tear on the flaps and is a contributing factor for cracking of the flap fittings that the flap actuators are attached to.

I read somewhere that the DHC-6 Twin Otter is capable of reversing its engines while in flight, apparently used on some short runways or extra steep approaches (e.g. St Bartholemew). Is this true or am i getting confused?

biggles

IIRC the Cessna Caravan 206, Casa 212 and Dornier 228 can reverse pitch in flight. I've only tried it in the 228.

Musang

I wouldn't recommend it on a Boeing 767 - Lauda Air comes to mind.

The Lauda Air crash was a result of asymmetrical thrust, The practice is truly dangerous though in all aircraft as you go from an airplane to a brick in a second. And woe to the pilot that finds one of the reversers did not work.

Oops.

Regarding inflight use of thrust reversers. You may or may not know that NASA astronauts use a Gulfstream II to simulate the landing profile of the Space Shuttle. They get to something like 30,000' and engage the thrust reversers. The resultant descent approximates that of the Shuttles.

HS121 Tridents were also cleared to allow reverse thrust during descent

The C-17 can deploy thrust reversers in-flight to perform a tactical descent. I've seen sustained vertical velocities in the neighborhood of -10,000 FPM.

PW4084

In-flight reversing was also possible on Concorde. It was only to be used in emergency decents though, as Concorde didn´t have any airbrakes/spoilers. You would only use the inboard engines (Engine 2 & 3) with idle reverse thrust.

I don't know if anyone who has posted has actually used reverse thrust in the air, but if I may comment on some of the postings that have been made.


...The practice is truly dangerous though in all aircraft...

No, it isn't.

It has been approved for use on several aircraft types by their manufacturer over the years, and by aviation authorities around the world.

Provided its use is approved by the aircraft flight manual, there is no reason not to use it within the limits laid down.

If it isn't approved by the AFM, don't even think about using it.


...you go from an airplane to a brick in a second...

No, you don't.

The drag on the aircraft increases, and you can use that increased drag either to decelerate, or increase the rate of descent, or a combination of both.

On the types I've flown with this facility, a combination of both usually worked best, as one could then keep the aircraft attitude about level whilst the manoeuvre took place.


...and woe to the pilot that finds one of the reversers did not work...

No, it wasn't a problem.

I've used a single thrust reverser, more than once, without any problems, as permitted by the AFM. The resulting swing, due to thrust asymmetry, was minimal and easily contained with a little rudder.

Of greater concern to us was the potential failure of a thrust reverser to return to forward thrust after being used in the air, and this failure was covered and practiced in the simulator as part of the conversion syllabus.

Whilst irritating, it was not a major problem, and, if unable to rectify it in the air (the most likely cause being low duct pressure in the actuation mechanism) the engine would be shut down prior to landing.


...In-flight reversing was also possible on Concorde. It was only to be used in emergency decents though...

Concorde did not use reverse thrust during an emergency descent.

This was for a variety of reasons, the main one being that it was not approved for use at supersonic speeds.


...Is this done only with 4 engined-planes?...

The HS121 Trident was a tri-jet that had reverse thrust available on the outboard engines.


...HS121 Tridents were also cleared to allow reverse thrust during descent...

Correct, and also, if required, during the approach and landing flare as well.

Regards

Bellerophon

Biggles20- I don`t think the Twin Otter can reverse inflight, but I`m not a 100% sure on that. The Dash8 forbids reverse inflight, there is a Godawful screaming horn that goes off if you try. The issue there is that the props can dangerously overspeed, causing gearbox failure. IIRC, there have been serious accidents with other aircraft, maybe King Airs or Brasilias involving unapproved inflight reverse.

The DHC-6 Twin Otter can indeed used propeller reverse in flight.
I have personally done so, with extreme caution, when the aircraft was introduced to a west coast commuter airline in the mid-sixties.
VERY high rates of descent were possible and, if one was proficient, very short landing (800 feet approximately) runs were possible, over 'obsticles' as high as 1500 feet close to the runway threshold.
The technique required the pilot to exit propeller reverse just prior to touchdown, with flaps set to 40 and an IAS of approximately 55knots (well below Vmc), as I recall.
The deHavilland demo pilots were very good instructors.

However, get it wrong, and the results will not be to your liking.

[Edited 2004-05-12 18:29:29]

Not related to in-flight reversing but on the subject of the Twotter there's a great video below of a takeoff from Lukla in Nepal. Very impressive TOR but not the best place to have a PT6 quit  


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Photo © Tobias Baertl


http://www.bazlinton.com/images/Lukla_2001.mpg (11 mb)

Further to my above comments about the DHC-6, it is my understanding that the aircraft AFM now contains a notation prohibiting in flight propeller reverse.
Just as well, as it requires extreme care, if used.
Further,
propellers on large aircraft require oil pressure to feather (unlike light aircraft), supplied via an electrically powered feathering pump (on large piston engine transport aircraft).
So important is this pump, that the power for same is supplied directly by the battery bus, not thru the normal electrical busses.
Failure to feather a propeller in the event of an engine failure or, inadvertant reverse of a propeller in flight can be VERY serious as it results in huge amounts of drag, which seriously affects the controlability of the aircraft.
For example, in large piston engine powered transport aircraft, if the prop could not be feathered, either due to feather pump failure or oil depletion in the feather pump line, the normal drill was to pull the fire handle, which (amoung other things) cuts off the oil supply to the engine, in the hope that the engine will seize, thereby reducing the extreme drag of the rotating propeller.
Controlable propellers are very critical in adverse situations, and need to be treated with respect.

Not that regulations matter when pilots like to tell their "there I was" stories, but here is a little interesting reading regarding two of the aircraft that were specifically mentioned in this post:

The CASA 212 has a solenoid that automatically blocks the power levers from being pulled below flight idle when the aircraft is in flight thus preventing the pilot from selecting reverse while the wheels aren't spinning. In fact, the FAA felt it was so important that they issued AD 92-13-51 which requires that a mechanic operationally check this system every 300 hours. Read all about it at:

http://www.airweb.faa.gov/Regulatory_and_Guidance_Library/rgAD.nsf/0/4384782992711E3E86256A1F006731F4?OpenDocument

More importantly (especially after reading how "cool" it was to do) the FAA issued AD 99-18-13 against the venerable Twin Otter which requires that a supplement be inserted in the AFM that prohibits the pilot from selecting reverse in flight. The following is an excerpt from that AD:

"SUMMARY: This amendment adopts a new airworthiness directive (AD) that applies to all de Havilland Inc. Models DHC-6-1, DHC-6-100, DHC-6-200, and DHC-6-300 airplanes. This AD requires amending the Limitations Section of the airplane flight manual (AFM) to prohibit the positioning of the power levers aft of the flight idle stop while the airplane is in flight. The AFM amendment includes a statement of consequences if the limitation is not followed. This AD is a result of numerous incidents and five documented accidents involving airplanes equipped with turboprop engines where the propeller beta was improperly utilized during flight. None of the incidents or accidents involved de Havilland Inc. Models DHC-6-1, DHC-6-100, DHC-6-200, and DHC-6-300 airplanes. The actions specified by this AD are intended to prevent loss of airplane control or engine overspeed with consequent loss of engine power caused by the power levers being positioned aft of the flight idle stop while the airplane is in flight."

The AD required that the following statement be added to the AFM limitations section:

"Positioning of power levers aft of the flight idle stop while the airplane is in flight is prohibited. Such positioning may lead to loss of airplane control or may result in an overspeed condition and consequent loss of engine power."

If you would like, you may read the AD in its entirety at:

http://www.airweb.faa.gov/Regulatory_and_Guidance_Library/rgad.nsf/0/DAB67D5B793CEFC186256A4E005DC44D?OpenDocument

Nothing like regulations and safety to take away the fun, eh boys???

Oh wait, there's more...I just couldn't resist:

The Cessna Caravan, which is actually a 208 (the 206 was recip powered and had a none reversible propeller) has the following AD issued against it:

http://www.airweb.faa.gov/Regulatory_and_Guidance_Library/rgad.nsf/0/A9625AACF07A80EA86256A4F004542AC?OpenDocument

That's AD 97-25-04, which contains the following statement:

"SUMMARY: This amendment adopts a new airworthiness directive (AD) that applies to all Cessna Aircraft Company (Cessna) Models 208, 208A, 208B, 425, and 441 airplanes. This AD requires amending the Limitations Section of the airplane flight manual (AFM) to prohibit the positioning of the power levers below the flight idle stop while the airplane is in flight. This AFM amendment will include a statement of consequences if the limitation is not followed. This AD results from numerous incidents and five documented accidents involving airplanes equipped with turboprop engines where the propeller beta was improperly utilized during flight. The actions specified by this AD are intended to prevent loss of airplane control or engine overspeed with consequent loss of engine power caused by the power levers being positioned below the flight idle stop while the airplane is in flight."

Sound familiar? Are you starting to get the idea that someone thinks this whole in flight reversing thing is a really bad idea?

In fact, even the mighty Dornier 228 has, yes, you guessed it, another AD. Try AD 97-22-09 which has the following statement:

"SUMMARY: This amendment adopts a new airworthiness directive (AD) that applies to all Dornier Luftfahrt GMBH (Dornier) Models 228-100, 228-101, 228-200, 228-201, 228-202, and 228-212 airplanes. This AD requires amending the Limitations Section of the Dornier 228 Pilot's Operating Handbook (POH) to prohibit the positioning of the power levers below the flight idle stop while the airplane is in flight. This POH amendment will include a statement of consequences if the limitation is not followed. This AD results from numerous incidents and five documented accidents involving airplanes equipped with turboprop engines where the propeller beta was improperly utilized during flight. The actions specified by this AD are intended to prevent loss of airplane control or engine overspeed with consequent loss of engine power caused by the power levers being positioned below the flight idle stop while the airplane is in flight. "

Might want to be careful about who you brag to with this whole reversing the 228 thing, don't you think.

Just food for thought...

With regards to the Lauda Air crash, would it be possible to continue to control an aircraft such as a 767 if thrust reversers accidentally deploy in flight? Are the alternate measures one can take in this situation?
Hardkor

I just wanted to say that Broke is 100% correct about what he mentioned concerning the DC-8. Not that he needs my endorsement, but I thought I'd chime in anyway.  

i've used the reverser inflight on the C208. i also know that on the ilyushins the reversers were opened to act as airbrakes but the engines were not spooled up.

When we do simulator training, one of the "worst-case-scenarios" is a thrust reverser deployment on takeoff. It is controllable. But an inadvertant thrust reverser deployment at M0.82 is a different story, as would attest the spirit of the Lauda pilots involved, if they could. So, to be truthful, the take-off scenario really isn't a "worst-case-scenario".

Resorting to the use of any form of "less than flight idle" in any aircraft with any sort of power plant, for normal operations, repeating: NORMAL operations is a scary and dangerous undertaking. Especially with wing-mounted engines, whether they be propeller or jets. Assymetry is a function of the centre-line of thrust. Tail mounted engine assymetry is thus less of a problem than wing mounted engine assymetry.

Using the examples above, most of the DH series of multi-engine aircraft are able to have reverse Beta deployed in flight, although the Dash 7 had the most agressive "counter" system built into its design.

But again, I beg the question, WHY would you ever use it? Once deployed, there is always the risk the deployment is irreversible. Small potatoes perhaps.

But given that most manufacturers produce ZERO performance numbers for inflight use of any form of reverse thrust, then any pilot who uses it places themselves and their employer in a high liability situation.

Wouldn't it be best to think-ahead of the ATC situation and admit "go-around" when necessary rather than place equipment, life and your own individual futures at risk?

Yikes!

Yikes!

You appear to take a very pessimistic and dogmatic view on the use of reverse thrust in the air, with phrases like ...place equipment, life and your own individual futures at risk... and ...a scary and dangerous undertaking...

I wonder if you have personal experience in the use of reverse thrust in the air, or are just basing your comments on the second hand accounts of others? I have used it, several times over the years, and, with respect, I disagree with many of the points you have posted.


...the use of any form of "less than flight idle" in any aircraft...for normal operations...is a scary and dangerous undertaking...

No, it isn't. On approved types there is nothing scary or dangerous about it.


...But given that most manufacturers produce ZERO performance numbers for inflight use of any form of reverse thrust...

Most manufacturers don’t, because they don't permit it.

Precisely the same reason that the manufacturer of my current type doesn't produce data for taking-off on grass or landing on water. That doesn't mean it's unsafe for other types to do either of those things.

Those manufacturers who do permit the use of reverse thrust in the air on their aircraft, in my experience, always publish data on it in the AFM.


...WHY would you ever use it?…

For the same reasons, and using the same care and airmanship, that you use the spoilers on your B757.


… Once deployed, there is always the risk the deployment is irreversible...

Just like your spoilers. Would you not use them just because there is always a risk that they might fail to retract?


...any pilot who uses it places themselves and their employer in a high liability situation...

Not so. The use of reverse thrust in the air, on an approved type like the one I flew into the USA for years, does not incur any dangers or problems, legal or aeronautical. Neither the pilots, the aircraft manufacturers, the airline, the aviation authorities, the insurers nor the company lawyers had any concerns about it.

In short, whilst the approval to use reverse thrust in the air may be an unusual feature, that exists on only a few types, on those aircraft for which its use is approved, it is both a safe and useful feature, with none of the problems that some would have you believe.

The use of reverse thrust in flight on a type where it is not approved, is a completely different matter, and is about as stupid an action as is possible in aviation. Should you survive, you deserve all that's coming to you.


Regards

Bellerophon


[Edited 2004-05-16 13:06:21]

On one of the from the flightdeck series of videos of Concorde, they use idle reverse thrust on 2 of the engines when decending into JFK.

If I can find the video again I'll try to post more details


Jamo

With respect, Bellerophon - granted there are types which historically have at one time or another allowed reverse while airborne. I do not dispute that you have used it legally or safely on approved types over the years.

The mini-discussion

...But given that most manufacturers produce ZERO performance numbers for inflight use of any form of reverse thrust...

Most manufacturers don’t, because they don't permit it.

My point exactly, reinforced by your closing statement in your post above.

I do not believe any current jet-transport manufacturer allows the inflight use of reverse thrust while airborne. To suggest that because you have used it and have not had a problem, in my opinion, is more of an historic reference rather than an advocacy of its use. Granted, when discussing the fringe type operations of which I used to be associated with (off-strip operations in arctic, desert, aerial survey, and oh-so-many-other non-airline ops) and I believe to which you may be referring, at least in part, these operations are more "frontier" areas where operators are still testing the limits of aviation.

As a line pilot in an airline operation though, the question of liability is at the forefront of my concerns everytime I go "below the line" on my pre-start checklist. It has to be. (Look at the KAL incident a few years back where a DC10 ran off the end of the runway during the F/O's botched takeoff attempt.)

And yes, I have experienced inflight use of this procedure many times on deHavilland turboprops. Thank you for asking.

Use of any procedure under normal circumstances for which you cannot justify with an AFM reference, and especially if there is an AFM reference prohibiting same, places the PIC in a very high liability issue should something go wrong. And things do go wrong from time to time.

Please don't misunderstand - I readily accept what you say about "approved types and procedures". My discussion deals solely with unapproved use of unapproved or unproven procedures on a normal or regular basis, as you state in your closing sentence:

The use of reverse thrust in flight on a type where it is not approved, is a completely different matter, and is about as stupid an action as is possible in aviation. Should you survive, you deserve all that's coming to you.

Best Regards,

Yikes!

The C-17 can deploy thrust reversers in-flight to perform a tactical descent. I've seen sustained vertical velocities in the neighborhood of -10,000 FPM.

All I can say I HOLY CRAP, that has got to be nerve racking!

The C-17 can deploy thrust reversers in-flight to perform a tactical descent. I've seen sustained vertical velocities in the neighborhood of -10,000 FPM.

All I can say I HOLY CRAP, that has got to be nerve racking!

Less nervewracking than being a sitting target for AA I guess but I see what you mean  

The docu on Discovery has a pilot interview. He mentioned -14000fpm. Yeeeha!

Yikes!

Thank you for your reply, I obviously misunderstood the point you were trying to make, as I agree with your views on the unauthorised or unapproved use of reverse thrust in the air.

I was just making the point, that on approved types, it was neither dangerous nor unsafe.

Of the two passenger jets I've used it on, one was also a De Havilland, as for the other, also built in the UK - what was it you suggested it could be ...a fringe type operation...?

Well, I suppose it might be described like that 

But it was great fun while it lasted! 

Regards

Bellerophon

With respect to the Lauda air accident, would there have been anything that the pilots could have done to control the situation? Or would reverse thrust at Mach 0.82 have been to difficult to overcome? Was it bad maintenance that led to this accident? Could it happen again now on a 767 or any other aircraft?
Any info would be greatly appreciated
Hardkor

There are a number of ADs re: the B767 thrust reversers requiring inspections and modifications to prevent anything like that happening again.

As for the controllability issue, i'd imagine the deployment of a reverser at near cruise speeds and cruise thrust levels would place HUGE loads on the aircraft. A quote from aviation-safety.net says: "One of the aircraft's wings was found 19km and the cockpit 1,5km from the main crash site." It's clear the aircraft wasn't in a good state well before it hit the ground.

This is probably a dumb question, but what does AD stand for, a directive of some sort?

AD=Airworthiness Directive

After Air Lauda 767 had a T/R deploy inflight and caused the aircraft to crash, at least all the 737's that I haved worked on, have T/R Sync Locks to prevent an accidental deployment inflight.