Asymetric Thrust
BAC 1-11 Asymmetric Reverse?
‘ Morning Green-dot,
Regret you may be − understandably − barking up the wrong tree. I think the BAC 1-11 incident you remember was a Dash200; landing on Rwy01R in 1981, in almost calm conditions. After a normal touchdown, the copilot, who was the PF, called for spoilers and full reverse iaw the SOP. The captain selected them and, as the Speys spooled up, and the nosewheels touched down, the aircraft swung alarmingly to the right. The aircraft was light, so the speed had already fallen to about 100kts. Also iaw SOPs, the captain immediately selected reverse idle, but the swing continued.
Meanwhile, the copilot had already selected full left rudder, which had no effect. [There is no rudder-fine (nosewheel) steering on Dash 200s.] Neither pilot attempted to arrest the swing using their steering handles; perhaps because the speed was above the 80-knot maximum in the SOP, and possibly because of the violence of the swing. The captain selected heavy left brake, but this seemed to make no difference to the continuing swing, and the aircraft left the right side of the runway; the captain shutting the engines down and operating the fire handles as it crossed a strip of grass and entered a ploughed (agricultural) field.
The aircraft had left the runway edge about 3 seconds after departing from the runway centreline. No one was hurt, and the 1-11 suffered little damage. The UK AIB investigated the incident, however. The FDR indicated that both engines and reversers had functioned correctly, and they were checked and found to be serviceable. Analysis of the tyre marks indicated that the nosewheels had been slightly offset as they touched down, but within the limits of system acceptability. However, they had apparently failed to caster straight in the normal way. Instead, they had remained fixed at an angle of about one or two degrees to the right. Some corrosion was found in the castering mechanism, but the proposed failure was never proven or reproduced, as far as I know.
Among other things, the incident did show the authority of undesired nosewheel-steering movements on a dry runway, particularly on short-wheelbase aircraft; the increase in its authority when mainwheel brakes are applied; and reminded us that rudder effectiveness is reduced when tail-mounted engines are in reverse thrust. It also taught us that, when your action seems to create a problem, the coincidence of the two events may be just that − a coincidence.
Regret you may be − understandably − barking up the wrong tree. I think the BAC 1-11 incident you remember was a Dash200; landing on Rwy01R in 1981, in almost calm conditions. After a normal touchdown, the copilot, who was the PF, called for spoilers and full reverse iaw the SOP. The captain selected them and, as the Speys spooled up, and the nosewheels touched down, the aircraft swung alarmingly to the right. The aircraft was light, so the speed had already fallen to about 100kts. Also iaw SOPs, the captain immediately selected reverse idle, but the swing continued.
Meanwhile, the copilot had already selected full left rudder, which had no effect. [There is no rudder-fine (nosewheel) steering on Dash 200s.] Neither pilot attempted to arrest the swing using their steering handles; perhaps because the speed was above the 80-knot maximum in the SOP, and possibly because of the violence of the swing. The captain selected heavy left brake, but this seemed to make no difference to the continuing swing, and the aircraft left the right side of the runway; the captain shutting the engines down and operating the fire handles as it crossed a strip of grass and entered a ploughed (agricultural) field.
The aircraft had left the runway edge about 3 seconds after departing from the runway centreline. No one was hurt, and the 1-11 suffered little damage. The UK AIB investigated the incident, however. The FDR indicated that both engines and reversers had functioned correctly, and they were checked and found to be serviceable. Analysis of the tyre marks indicated that the nosewheels had been slightly offset as they touched down, but within the limits of system acceptability. However, they had apparently failed to caster straight in the normal way. Instead, they had remained fixed at an angle of about one or two degrees to the right. Some corrosion was found in the castering mechanism, but the proposed failure was never proven or reproduced, as far as I know.
Among other things, the incident did show the authority of undesired nosewheel-steering movements on a dry runway, particularly on short-wheelbase aircraft; the increase in its authority when mainwheel brakes are applied; and reminded us that rudder effectiveness is reduced when tail-mounted engines are in reverse thrust. It also taught us that, when your action seems to create a problem, the coincidence of the two events may be just that − a coincidence.
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Morning Chris,
You are correct. Sorry for the mix-up between 01L and 01R
. Indeed it was 01R and the incident happened right in front of us while we were working on the appron at the Schiphol East hangar area.
Thanks for your detailed explanation regarding this incident. The only reference to the incident for me at the time was the press who in the papers I read and in the news on TV all referred to a malfunctioning reverser, I never read a copy of the final report. Having grown wiser over the years and having learned to take the press with a grain of salt regarding anything they write about aviation (and just about any subject for that matter) I stand corrected.
Regards,
Green-dot
Regret you may be − understandably − barking up the wrong tree. I think the BAC 1-11 incident you remember was a Dash200; landing on Rwy01R in 1981, in almost calm conditions.
You are correct. Sorry for the mix-up between 01L and 01R
. Indeed it was 01R and the incident happened right in front of us while we were working on the appron at the Schiphol East hangar area.Thanks for your detailed explanation regarding this incident. The only reference to the incident for me at the time was the press who in the papers I read and in the news on TV all referred to a malfunctioning reverser, I never read a copy of the final report. Having grown wiser over the years and having learned to take the press with a grain of salt regarding anything they write about aviation (and just about any subject for that matter) I stand corrected.
Regards,
Green-dot
