The LUXAIR F50 Crash Cause

Re the Der Spiegel Article Below

Quite likely to be the LUXAIR F50 accident cause because of the appearance of the wreckage (virtually fell straight down as if it had lost airspeed very rapidly - as it surely would if it experienced GROUND IDLE in flight.
No sane pilot is going to lift a guard and select power-levers to ground-fine whilst airborne (that's a very definite action in any turboprop).  In fact Ground fine is an F-27 term, whereas on the F50 Ground Idle equates to the start of the beta range (alpha range being the flight range in most turboprops and very positively divides forward thrust from the reverse thrust commencing at the top of the beta range).


It's far more likely that another selection on the centre console (flap perhaps, but may have been anything?) caused an electrical short and removed the beta stop baulk, allowing the pilot's reduction to low Flt Idle power to "go through" into ground idle. Or maybe the short was there all along and the baulk just wasn't there. I would guess that a box swap-out may have occurred on that centre console during the "technical check the day before".... and that could have set up a short (or the makings of a short). But they'd fall out of the sky really quickly if both had gone into GI.

Really needs a further explanation for why they were so far right of the final approach course for the ILS and heading even further right. So it may have been that the excursion into Ground idle occurred on only one engine (i.e. he didn't bang both against the "disappeared stop" and only one, the RH one, went through). The asymmetrics would have then taken them (and their heading) right of course. I'm not sure whether immediate feathering action is available on an engine with its prop stuck in ground idle. Would it possibly be inhibited? And how feasible is a quick reselection of the Flight Range (assuming that they tumbled to what had happened?)

Can a tripped CB remove that GI baulk? All good questions that remain to be answered.

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Up until the point where this info came out, it was a quite confusing accident (and aren't they all). It's now falling into place and may well have been a wiring-related/electrical cause - because that GROUND IDLE BAULK is a solenoid-operated electrical device (weight-on-wheels or manual override).
So either:
 
a.  the technicians left the CB (for the baulk) out during the previous day's servicing (and the pilots didn't notice  it out ) or
 
b.  the CB had shorted out itself out (or tripped enroute) or
 
c.  There was a short that kept the baulk in absentia through-out  or
 
d.  There was a shorting-out (that removed the GI baulk) when a flap handle (or something else was moved - at about 1000ft AGL on finals).

e.  The pilot had intentionally selected Ground Idle  (unlikely)

 
All it would have then taken was a power reduction to against that non-existent GI stop and the one (or both) P/L's could go through (into GI). However some turbo-prop aircraft have an additional soft-stop that must be overridden airborne (pulled through - but needs brutish force). I'm not sure whether that's the case for the F50. I'd doubt it actually.
I It still seems (prima facie) to best be an electrical explanation. Finding evidence of that may be possible as the cockpit was about 75% intact.

   The Relevant AirWorthiness Directives (for the Flight Idle Stop Hazard)


   Four Very Similar CASA 212 accidents
November 23, 2002 - Luxair Disputes Magazine's Crash Report
BERLIN, Germany- Pilot error could be to blame for the fatal Luxair plane crash near Luxembourg's airport earlier this month, a German magazine reported on Saturday, but the airline called the report speculation.

Der Spiegel weekly said in a report issued before Sunday's publication that flight recorder data showed both propellers of the Fokker 50 were on a setting for taxiing, not for flying. This could have caused the plane to crash as it came in to land, killing 20 of 22 people aboard, it said.

Paul Greis, spokesman for Luxair in Luxembourg, rejected the report.

"I have not seen the article itself, but from the media reports I can say it is pure speculation," he said. "We do not have any information from the investigation team."

Without citing its information source, Der Spiegel said the propellers could not be mistakenly moved from the so-called "flight idle" setting to "ground idle" because the switch to make the change was covered by a protective flap.

Der Spiegel said the plane's manufacturers explicitly warned in their handbook against putting the propellers on to the "ground idle" setting during landing.

The plane smashed into a field in thick fog about five km (three miles) from Luxembourg's international airport when it was on landing approach on November 6. The dead were 15 Germans, four Luxembourgers and one French.

French passenger Jean-Daniel Boye escaped with light injuries, while the Luxembourg pilot, Captain Claude Poeckes, suffered serious but not life-threatening injuries.

Visibility was about 100 metres (300 feet), and five planes had landed safely at the airport before the Fokker 50.

Poeckes had been flying with Luxair for about seven years. The plane had been in service since 1991 and had had a technical check the previous day, according to the airline.

The crash was the first in the 40-year history of Luxair, which is 13 percent owned by the German airline Lufthansa and 36.5 percent by the Luxembourg government. The rest is held by private companies and the Luxair Group.