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.
Received a copy of this last night from my dad as well. But, like many of you have already stated, I was fairly certain they would have intercepted from the left, and if the avionics are anything like that of the mighty saabypoo, the GS will not capture until the LOC does.
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.
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.
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.
The dash 8 will not even capture the glideslope unless the loc is already captured anyway.
Even then it would not pitch up 30 degrees to capture either. If I recall correctly it doesnt even capture until it is within a 1 1/2 dot scale or so.
Ya... the RJ is the same way. It won't capture the GS until the localizer is captured. The 737, though, WILL capture the GS before it captures the localizer hence the memo given to the Southwest pilots. At Delta, we were trained to not arm APPR mode until the localizer is captured. I'm sure Southwest does the same thing, but it's nice to have a "heads up."
Still, this makes you wonder if this might have been a factor in the Colgan accident.
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.
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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.
Ya... scary stuff. A friend of mine was flying the Brasilia when he had the autopilot start aggressively banking and pitching the aircraft. They had to pull the circuit breakers to get control. After they landed, the mechanic pulled the autopilot panel and found soda had been spilled on it! In other words, there are a lot of possibilities.
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.
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