LET 410 crash in Russia
 

Khabarovsk Airlines flight 437 operated by L410 RA-67047 has crashed on approach to Nelkan airport killing six of the seven people on board. The flight originated at Nikolayevsk-na-Amure.

https://www.rt.com/news/409892-plane...hild-survived/
https://aviation-safety.net/database...?id=20171115-0

Aviation Herald:
Crash: Khabarovsk L410 at Nelkan on Nov 15th 2017, impacted ground short of runway

How on earth does a propeller go into reverse in flight?

Crash: Khabarovsk L410 at Nelkan on Nov 15th 2017, impacted ground short of runway, right propeller went into reverse in flight

Don´t know anything about LET systems, but Swearingen Merlin accident long time ago in Finland was caused by very worn power lever linkages/gates which allows pilot pull prop to REV during approach. (which was kind of unstable HOT and HIGH in bad weather)

Sadly, this accident claimed lives.

Not the first time.

https://en.wikipedia.org/wiki/Northw...nk_Flight_2268

How on earth does a propeller go into reverse in flight?


https://www.flightglobal.com/news/ar...-crash-170741/

Those seem to be commanded beta range accidents. No suggestion that this one was commanded.

Luxair F50:-

http://www.mt.public.lu/ministere/services/coordination_generale/AET/aviation/pdf_EN_fokker.pdf

Suspension of type is recommended until malfunction cause will be investigated. Locally yet.

https://aviation-safety.net/database...?id=19960212-0

This aircraft also had the right engine go in reverse right after take-off, although it does not say so here.

L-410 RA-67047 15.11.2017

The Investigation team of the L410 UVP-E20 RA-67047 aircraft fatal accident continues its work at the accident site. Preparations for the aircraft and engines transportation to the examination facilities are being conducted. The team of experts from the Czech Republic, participating in the investigation work, includes the representatives from Ge Aviation Czech (engine manufacturer).

The Investigation team has performed the downloading and readout of the flight recorders' data. The obtained flight data and voice records are being analyzed by experts of the IAC laboratory.

Based on the preliminary information it is found that during the final stage of the approach to Nelkan landing site, at height of 150 meters, the abnormal situation developed, related to the right power plant operation. Further, the aircraft lost the speed, the right roll was developed (the FDR recorded the bank angle over 180 degrees), and with-the-ground collision occurred. The flight crew attempts to counteract the roll tendency had failed.

The left engine was operating normally. There was no engines' in-flight shutdown.

All the necessary information for the flight safety measures implementation has been provided to the competent civil aviation authorities.

The Investigation team together with the accredited representative of the Czech Republic and specialists from the aircraft (Aircraft Industries) and engine manufacturers continues to work out all possible circumstances of the fatal accident.

Given some of the comments and terms used regarding this incident, I would like to clarify for the non-aviation and non-technical posters that the engine doesn't go into reverse, nor does the propellor stop and then reverse direction.

Reversible propellers—those where the pitch can be set to negative values—can also create reverse thrust for braking or going backwards (on the ground) without the need to change the direction of shaft revolution.

Sad to hear about this incident.

I just made a thread about this kind of nightmare about 2 months ago. Strongly suggest everyone take a look at it, as there is a lot of good info about what to do if this happens to you.

Pretty much the same way a turbojet/fan thrust reverser can deploy in flight (Lauda Air 004, TAM 402) - something breaks, either in the primary operating system, or the safety interlocks, or both.

As evansb alludes to, a prop goes into reverse thrust simply by rotating the pitch of the prop blades from a position/angle that pushes air backwards (forward thrust) to a position/angle that pushes air forwards (reverse thrust).

As in, from <\ to </ (direction of aircraft travel <<<<). A matter of a relatively few degrees from one direction to the other.

This is a PT6/Hartzell prop hub (although schematic and not necessarily identical to that in the LET) - as you can see, the system operates on oil pressure, pistons, valves, springs, levers and a governor (rpm sensor/limiter).


https://i.ytimg.com/vi/tIAfmY42siI/maxresdefault.jpg


It shouldn't happen - it is not supposed to happen - but I expect one can see where a piece of metal snapping or an oil clog at the wrong moment can end with the prop blades blowing air in the wrong direction.

Bear in mind also that (despite Avherald not understanding the difference between the two) reverse and beta aren't synonymous.

A prop doesn't need to go fully into reverse to cause this kind of accident - anywhere in the beta range (that's to say below flight idle) will result in severe embarassment if it's applied on one side only of a twin.

If the cause turns out to be a failure of the pitch change mechanism, that will typically result in the forces on the blades tending to fine them off, with a consequent massive increase in drag on that side and potentially catastrophic results unless the prop can be quickly feathered.

On the trusty old Saab 340s decades ago, the only protection from inadvertent ground idle beta was a little metal guard that flipped into position on the prop levers after advancing them past ground idle.

for those not familiar, beta = pitch angle of the prop blade. set it too shallow, and you’re essentially placing a 2m or so diameter solid disc out on the wing with all the resistance that causes. cant be recovered unless feathered.

On quite a few engines in flight it can't even be recovered by feathering.

Most work by dumping the oil pressure in the hub and a big spring pushes the props to feather.

With the flight aerodynamic loads the spring is not powerful enough to get the props out of beta range towards feather.

There was a similar accident in 1995: Accident L-410UVP of the Ukrainian Airlines near Providence. // AirDisaster.ru

Also there is a rumor that last words on CVR was "WTF? Reverse?"

I'm not familiar with the propeller reversing system on the LET 410. However, in general, it is correct that "reverse" and "beta" are two different things. Both will result in reverse blade angle upon pilot command, but how it got there is different.

For my experience beta systems have a guard or gate to prevent inadvertent selection out of "forward". Some of those systems can be overridden by the pilot in flight, others not. Barring mechanical failure, beta (flat pitch, or reverse blade angle) selection will be the result of the pilot moving the engine power level aft. I would credit a pilot with not selecting only the right engine into reverse in flight.

There have been numerous accidents resulting from eager pilots selecting lots of beta upon touchdown, to achieve a short landing. It has happened that one propeller did not enter the beta blade angle, and the asymmetric thrust resulted in a loss of control on the ground. I speculate that some turbine parachuting aircraft may be operated in beta range coming down following the jump run.