Originally Posted by
noneya
Has anyone noticed that the thrust reverser on the right engine in missing? Take a look at the picture:
http://c.o0bg.com/rf/image_960w/Bost...crash5_met.jpg Looking at it close up, it is clear the the reverser is missing from the right engine, but is in place on the left engine. Owen, The thrust reverse's are fully intact in the picture you posted. The only thing missing is the close out cover on the right actuator from what I can see. that seems to answer the flap question. though oddly put that the flaps were set in the cockpit to 10. wondering if the flaps were actually at 10 glendalegoon, On the GIV it is not uncommon to takeoff flaps 10 (think there was a whole tread on this some time ago). The aircraft also will give you a configuration warning if the flap are not at least 10 degrees and the throttles are advanced..... It is possible they forgot to set flaps 20 when they taxied out and only had them at flaps 10. It is very common to taxi in with flaps left at 10 so you can inspect the flap tracks actuators during the walk around. But I would suspect something else other than flaps, or in combination with, because even if they wanted 20 and only had 10 the aircraft would have flown with no problems, the runway is plenty long enough. J
Not a GIV pilot, but I am a GIV mechanic and avionics tech.
Yes, the R/H engine T/R is present. The outboard stang fairing that covers the actuator has been torn off, but both upper and lower doors are there. The lower door appears to be hanging down a few inches. Based on their appearance in the photo, it's difficult to say if they had been deployed or not. During ground maintenance, if we deploy them, and then shut off pressure from the hydraulic ground service cart -- after a few minutes, (once the pressure in the aircraft hydraulic lines has dropped to zero), the doors can be pushed closed by hand. Takes a bit of muscle power, but definitely do-able.
I would think that with the disintegration of the airframe as the aircraft departed the runway, the hydraulic systems would have been breached almost immediately, and with the loss if pressure, combined with the rapid deceleration of the aircraft, the T/R doors could have swung forward and shut, even if they had been deployed. Then again, perhaps they never were deployed in the first place. Hopefully the FDR will shed some light.
Flaps 10 or 20 are both authorized for takeoff, though I believe a flaps 20 takeoff is far more common. However, during the crew's preflight initialization of FMS performance data, on the Takeoff Init page 3, they have to enter which flap setting is going to be used. As far as I know, the default flap setting on this page is Flaps 20, and the crew would have to specifically hit the 3R line select key "OR 10" to tell the perf computer that a flaps 10 takeoff is planned.
If the FMS takeoff Init had been left at the default flaps 20, and the flaps had inadvertently only been deployed to 10 degrees, the v-speeds would not have "boxed", and there would have been a large yellow "VSPD" caution flag next to the airspeed tape on the pilot's PFD display. Checking that V-speeds are valid is a standard part of the crew's checklist prior to taking the runway, and I doubt that it could have been missed.
In other words, if they indeed started the takeoff roll with flaps 10, I have to think that it was their specific intention to use flaps 10, or they would have noticed the missing V-Speeds before ever advancing the power levers.
There is also a separate takeoff config alarm system, which is operated by microswitches which is activated when the power levers are advanced beyond a certain point. This will give a triple-chime master warning tone and light, as well as a red CAS message if the power levers are advanced and the flaps position sensors detect that the flaps are either less than 10, or greater than 20 degrees.
Now, I HAVE seen this system fail. I don't know if GIV crews routinely test the takeoff config system as part of their preflight cockpit flows, but there is a maintenance requirement to do a functional test of the system every 12 months. We had an early-model (1989) GIV, and when I performed the test in the hangar when it came due, lo and behold, there were no warnings, even with both PLs fully advanced, and the flaps fully up.
It turned out that the microswitches on both the left and right power lever sectors had failed - probably due to age. I remember it particularly well, as accessing and changing the switches was an absolute b***h of a job, due to their location.
I would not want to speculate as to what might have happened in this accident, other than the obvious fact the aircraft departed the end if the runway at high speed without becoming airborne. I do hope that the CVR and FDR will have recoverable data, that will shed light on what may have happened, as this kind of tragedy is shocking to all of us who maintain and fly the GIV.