B727 undershoot accident at Pohnpei, Micronesia in 2008
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B727 undershoot accident at Pohnpei, Micronesia in 2008
In 2008 a Boeing 727 overran the runway and into the sea at Pohnpei, Micronesia. A question was recently placed on the North American Forum seeking the NTSB report on this accident.
One reply said this:
2008 was Asia Pacific Airlines N319NE... AntiSkid sensor malfunction caused system to continuously release brakes on landing. Aircraft overran runway and came to rest with nose wheel in water. Returned to service 6 months later.
Is this type of defect feasible in 737 Classics? If so, it may be the basis for a simulator exercise. Has any reader heard of similar incidents involving anti-skid sensor malfunction?
One reply said this:
2008 was Asia Pacific Airlines N319NE... AntiSkid sensor malfunction caused system to continuously release brakes on landing. Aircraft overran runway and came to rest with nose wheel in water. Returned to service 6 months later.
Is this type of defect feasible in 737 Classics? If so, it may be the basis for a simulator exercise. Has any reader heard of similar incidents involving anti-skid sensor malfunction?
Last edited by Centaurus; 9th July 2013 at 13:58.
Joined: Apr 2008
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From: nowhere
Does your 737 have the Hydro-Aire Mark III anti-skid system which seems to be what many if not all 727's have installed?
If so, then "each tire has a wheel speed transducer, a little generator that produces power proportional to the speed of the tire. This goes to a control shield which interprets this signal as wheel speed. It is then compared to another tire. If the signal degrades (speed drops) on any given tire in comparison to its reference tire, an electrically operated hydraulic control valve limits the amount of hydraulic pressure available to the brake for the tire that is skidding. If the skid goes into a full scale locked wheel situation, pressure can be completely cut off. Then, as the wheel speed of the skidding or locked wheel approaches the speed of the reference wheel, pressure is slowly reapplied. The whole process should take about 20 seconds."
By the way, Boeing invented the anti-skid system and then licensed it to brake vendors, ie Hydro-Aire.
Other aircraft such as the HS-748 and Caravelle had Dunlop Maxarets for protection. These were all-mechanical.
If so, then "each tire has a wheel speed transducer, a little generator that produces power proportional to the speed of the tire. This goes to a control shield which interprets this signal as wheel speed. It is then compared to another tire. If the signal degrades (speed drops) on any given tire in comparison to its reference tire, an electrically operated hydraulic control valve limits the amount of hydraulic pressure available to the brake for the tire that is skidding. If the skid goes into a full scale locked wheel situation, pressure can be completely cut off. Then, as the wheel speed of the skidding or locked wheel approaches the speed of the reference wheel, pressure is slowly reapplied. The whole process should take about 20 seconds."
By the way, Boeing invented the anti-skid system and then licensed it to brake vendors, ie Hydro-Aire.
Other aircraft such as the HS-748 and Caravelle had Dunlop Maxarets for protection. These were all-mechanical.
