ILS 23 in BUF
02-19-2009 | 07:17 AM
#22
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Just had this sent to me.....
Safety Alert 2009-1
BUF ILS Hazard
SWAPA Pilots,
There is a potentially significant hazard concerning the ILS to runway 23 in BUF.
Information has been received indicating it is possible to obtain a significant nose pitch up, in some cases as much as 30 degrees, if the glide slope is allowed to capture before established on centerline. Pilots who are preparing to configure and land have the potential to experience abrupt pitch up, slow airspeed, and approach to stall if conditions present themselves in a certain manner.
This effect is the result of an earthen obstruction close enough to the ILS to affect the integrity of the glide slope signal. This has resulted in the issuance of an advisory given on ATIS which states that "the ILS Glide Slope for runway 23 is unusable beyond 5 degrees right of course."
When attempting to intercept the runway 23 ILS from right traffic, the ILS glide slope indication may read full deflection down. Just prior to intercept it may then move up in such as manner as to enable approach mode to capture in such a way as to result in a nose up pitch and loss of airspeed.
Southwest Airlines has issued a notice reading: "Until further notice, when executing the KBUF ILS/LOC Runway 23, DO NOT select Approach Mode until established on the localizer inbound."
This issue is being addressed on several levels in an attempt to address procedures, facilities, and communication regarding this matter. If you experience any issues related to this, please file an ASAP form and or call SWAPA Safety at SWAPA toll free.
02-19-2009 | 07:45 AM
#23
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From: 737/FO
In 2004 in the SAAB I had a false loc/gs capture going into PWM. We were maybe 6 miles south of the ILS 11, due south of AIMME, at about 5000 ft day VFR. The autopilot was engaged and the approach mode armed. The loc and gs captured. Chasing the signals the aircraft instantly and suddenly pitched down about 10 degrees, maybe a little more, and banked to the right. I clicked off the a/p and recovered. It was disconcerting to say the least.
02-19-2009 | 08:06 AM
#25
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In 2004 in the SAAB I had a false loc/gs capture going into PWM. We were maybe 6 miles south of the ILS 11, due south of AIMME, at about 5000 ft day VFR. The autopilot was engaged and the approach mode armed. The loc and gs captured. Chasing the signals the aircraft instantly and suddenly pitched down about 10 degrees, maybe a little more, and banked to the right. I clicked off the a/p and recovered. It was disconcerting to say the least.
02-19-2009 | 08:38 AM
#26
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Why would you arm the approach that far off course? AIMEE is more than 16 miles from the loc antenna. The service volume is 35 degrees to 10 miles and 10 degrees to 18 miles. If you were 5 miles south of the loc you were outside the 10 degree service volume. My airline requires the localizer to be armed and captured before selecting the approach mode. I've seen the flight director do some weird things but arming an approach that far out is just asking for trouble.
02-19-2009 | 10:08 AM
#27
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From: DAL Pilot
Still, this makes you wonder if this might have been a factor in the Colgan accident.
02-19-2009 | 10:08 AM
#28
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From: SIC
I've seen phantom localizers as well, and watched the autopilot capture and try to follow it, there are a couple airports that it's happened at, but i cant remember which ones. Also had a situation in MKE with a localizer bouncing moving from side to side, half scale deflection and immediately back the other way.
02-19-2009 | 10:12 AM
#29
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From: DAL Pilot
In 2004 in the SAAB I had a false loc/gs capture going into PWM. We were maybe 6 miles south of the ILS 11, due south of AIMME, at about 5000 ft day VFR. The autopilot was engaged and the approach mode armed. The loc and gs captured. Chasing the signals the aircraft instantly and suddenly pitched down about 10 degrees, maybe a little more, and banked to the right. I clicked off the a/p and recovered. It was disconcerting to say the least.
02-19-2009 | 10:41 AM
#30
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From: Engines Turn or People Swim
It should be simple for the NTSB to determine if the pitch up occurred before or after the AP disengaged.
This is ILS glitch is interesting, but my gut feeling is that neither a modern airplane nor a professional crew would allow a GS to put them in an uncontrollable flight regime.
This is ILS glitch is interesting, but my gut feeling is that neither a modern airplane nor a professional crew would allow a GS to put them in an uncontrollable flight regime.
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