B727 - Approach
Thread Starter
Joined: Sep 2001
Posts: 3
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From: USA
B727 - Approach
To all the left seat boffins: We recently had a B727-200 land at an extremely low glideslope angle.
Post incident FDR readout-indicated 2 touchdowns 4+ secs apart, with no significat registration of vertical descent G and with immediate deceleration to a stop after the second touchdown. Reversers were not deployed. 3 main tyres were blown, LH strut collapsed and 4 brakes were W/O. (Plus someones very precious runway was blocked for 3+ hours!).
Post flight the anti skid tested S. It appears that the anti-skid was "fooled" into thinking the aircraft was on the ground by the "skip-spinning" of the mainwheels after the first touchdown. Is there a recommended minimum approach angle for the type?
Has anyone encountereed a similar situation?
Any other comments (printable!)
Post incident FDR readout-indicated 2 touchdowns 4+ secs apart, with no significat registration of vertical descent G and with immediate deceleration to a stop after the second touchdown. Reversers were not deployed. 3 main tyres were blown, LH strut collapsed and 4 brakes were W/O. (Plus someones very precious runway was blocked for 3+ hours!).
Post flight the anti skid tested S. It appears that the anti-skid was "fooled" into thinking the aircraft was on the ground by the "skip-spinning" of the mainwheels after the first touchdown. Is there a recommended minimum approach angle for the type?
Has anyone encountereed a similar situation?
Any other comments (printable!)
Joined: Feb 2002
Posts: 554
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From: The Sandpit
A low approach angle will almost certainly result in a higher approach speed. This combined with a 4+ sec bounce (which is an extremely long bounce possibly exaserbated by the high approach speed) would mean that at the second touch down there would not be a lot of runway left!! (the bounce alone would account for over 300 yards of runway)
I concur with NSF in that the damage was caused by max braking. Even with a fully serviceable a/skid system the energy dissipation due to an RTO or max braking on landing can blow tyres (especially if they are at or close to MM limits), melt fuses, deplete brakes, etc
I concur with NSF in that the damage was caused by max braking. Even with a fully serviceable a/skid system the energy dissipation due to an RTO or max braking on landing can blow tyres (especially if they are at or close to MM limits), melt fuses, deplete brakes, etc
Thread Starter
Joined: Sep 2001
Posts: 3
Likes: 0
From: USA
Mono, NSF thank you for the reply:
The aircraft came to rest some 2/3rds of the way along a 10,000 ft runway. The wheels and brakes were ground down to just below the wheel brake pad rotors and stators. The recorded touchdown speed was 145 knots (considered high for the configuration)
It is our conjecture that due to the extremely shallow approach - after the initial touchdown the aircraft became airborne - the PIC pushed the nose forward thinking he was fully grounded - when in fact the recorder shows the MLG to be off the ground at this point - The nose wheel touched down hard (recorder) and we think the PIC then applied full braking - shortly after this event the MLG touched down with the brakes locked (as they would be) and the rest as they say is history.
The aircraft came to rest some 2/3rds of the way along a 10,000 ft runway. The wheels and brakes were ground down to just below the wheel brake pad rotors and stators. The recorded touchdown speed was 145 knots (considered high for the configuration)
It is our conjecture that due to the extremely shallow approach - after the initial touchdown the aircraft became airborne - the PIC pushed the nose forward thinking he was fully grounded - when in fact the recorder shows the MLG to be off the ground at this point - The nose wheel touched down hard (recorder) and we think the PIC then applied full braking - shortly after this event the MLG touched down with the brakes locked (as they would be) and the rest as they say is history.
