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Icing tape - lessons learned.
"Jay Honeck" wrote in message
ups.com... This is the audio tape of a Fed Ex Caravan pilot who tangled with some severe icing conditions. http://www.alexisparkinn.com/photoga...78L-Mayday.mp3 (It's a good-sized .mp3 file, so be patient while it downloads...) This was given to me by our local FAA safety guy, to share with our airport user's group. The stark terror in her voice is chilling, and really points out how quickly things can go bad. -- Jay Honeck Iowa City, IA Pathfinder N56993 www.AlexisParkInn.com "Your Aviation Destination" Ok, since the previous thread has degenerated into a urinating contest about the tone of the pilots voice - I will start a new thread in an attempt to discuss what could be learned from this incident. (And, yes I was one of the guilty parties.) 1) I suspect (knowing nothing beyond what I heard) that the pilot failed to recognize the ice buildup untill control was lost. I ASSUME that she was in the soup at the time - so the lesson here is pay attention - it's cold, you are in the clouds, look out the window and watch for ice. Right? 2) Don't give up the ship. Even after loosing control, loosing lots of altitude, etc. She kept fighting, figgured out what was wrong, applied the appropriate counter measures (boots and heat - albeit a bit late) and got it back. She also managed to give the "look out below" warning to ATC. 3) Instruments lie. It sounds like the peito (how the heck do you spell that - I've tried a dozen different ways and none of them look right) froze (she said she couldn't control airspeed). Knowing that she had a load of ice would, I think, make one suspect the IAS and I would think that the sound and feel of the aircraft should have helped her realize that the actual airspeed was OK? Of course the ice would have effected the handling and made it more difficult to know exactly what was lying to her. A quick switch to alternate static might have been in order (She may or may not have done that) or a cross check with GPS (which I assume she had) might have been a good idea too (she may or may not have done that also). How do you know WHICH instrument is lying to you? You have to ignore your inner ear, but sound and feel? What else? Disclaimer - I ain't never flown with anything more than a hint of ice (the rain drops stopped moving on the windscreen). And I've never flown in IMC or with de-ice equipment. -- Geoff The Sea Hawk at Wow Way d0t Com remove spaces and make the obvious substitutions to reply by mail When immigration is outlawed, only outlaws will immigrate. |
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Icing tape - lessons learned.
On 2/6/2007 6:28:30 PM, "Capt. Geoffrey Thorpe" wrote:
3) Instruments lie. It sounds like the peito (how the heck do you spell that - I've tried a dozen different ways and none of them look right) pitot -- Peter |
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Icing tape - lessons learned.
On 2/6/2007 6:28:30 PM, "Capt. Geoffrey Thorpe" wrote:
A quick switch to alternate static might have been in order (She may or may not have done that) or a cross check with GPS (which I assume she had) might have been a good idea too (she may or may not have done that also). How do you know WHICH instrument is lying to you? You have to ignore your inner ear, but sound and feel? I replied too fast. To comment on your above: I have had my pitot heat fail during night IMC flight through wet snow in a Bonanza V35. The first indication to me that there was a problem was that the airspeed indication slowly but noticably fell from my cruise of 165 its to 140 and continued to fall. The first thing I did was check the GPS ground speed to confirm my speed was still roughly the same as it had been throughout the flight. I then double-checked and recycled my pitot heat switch to see if perhaps the switch was not on (it was) or had faulted. With indicated airspeed still falling, I then swiped the circuit breakers to see if one had popped - None did. With those cross checks, I came to the conclusion that the pitot heat itself must have failed and therefore ignored the ASI. This was confirmed after I landed by the touch test. Alternate static won't help a frozen or otherwise blocked pitot tube, BTW. In regards to the pilot of the Caravan, her brain was already oversaturated by the crisis of the aircraft stalling and falling. It is understandable to me that her brain did not register that perhaps the pitot heat was not on or had failed. I had the luxury of only having to deal with that one problem; the Caravan pilot had a much bigger problem on her hands. Sound and g-forces are a good secondary indication that the aircraft is in an unusual attitude, but I am pretty confident that I would not be able to recover my aircraft by sound and g-forces alone. In her case, again, her aircraft was probably unrecoverable for a short period due to icing and perhaps a misconfigured autopilot (a/p was probably flying the majority of the leg and was allowed to take the aircraft into the stall due to icing before the pilot noticed), so her instruments, other than her ASI, were not lying to her. I am surmising that it wasn't until she reached warmer air, released the a/p, and lost some of the ice that she was able to recover. -- Peter |
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Icing tape - lessons learned.
On 2/6/2007 6:55:26 PM, "Peter R." wrote:
In her case, again, her aircraft was probably unrecoverable for a short period due to icing and perhaps a misconfigured autopilot (a/p was probably flying the majority of the leg and was allowed to take the aircraft into the stall due to icing before the pilot noticed), Sorry, I should have written: misconfigured TRIM due to a/p... -- Peter |
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Icing tape - lessons learned.
Peter R. wrote : With those cross checks, I came to the conclusion that the pitot heat itself must have failed and therefore ignored the ASI. This was confirmed after I landed by the touch test. A good way to troubleshoot pitot heat is to watch the ammeter when you switch it on. Most pitot heat systems have a hefty current draw, which is readily apparent when you turn it on. No movement on the ammeter generally equates to no heat. I also use the ammeter to check my landing light whenever I turn it on (it's out in front where I can't see it). John Galban=====N4BQ (PA28-180) -- JGalban Posted at www.flight.org |
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Icing tape - lessons learned.
"Peter R." wrote in message
... On 2/6/2007 6:28:30 PM, "Capt. Geoffrey Thorpe" wrote: .... Alternate static won't help a frozen or otherwise blocked pitot tube, BTW. Right. But if you aren't sure what the problem is... In regards to the pilot of the Caravan, her brain was already oversaturated by the crisis of the aircraft stalling and falling. It is understandable to me that her brain did not register that perhaps the pitot heat was not on or had failed. I had the luxury of only having to deal with that one problem; the Caravan pilot had a much bigger problem on her hands. No kidding. Gotta give her credit for pulling her butt out of the fire. Sound and g-forces are a good secondary indication that the aircraft is in an unusual attitude, but I am pretty confident that I would not be able to recover my aircraft by sound and g-forces alone. I would agree. I was just thinking if sound and G were "ok" then perhaps it may have pointed to the airspeed as the bad actor. In her case, again, her aircraft was probably unrecoverable for a short period due to icing and perhaps a misconfigured autopilot (a/p was probably flying the majority of the leg and was allowed to take the aircraft into the stall due to icing before the pilot noticed), so her instruments, other than her ASI, were not lying to her. I am surmising that it wasn't until she reached warmer air, released the a/p, and lost some of the ice that she was able to recover. It isn't clear from the tape at what point she switched on the anti-ice, but she did say she had an OAT of 0 C. after she leveled off - doesn't sound like a lot of "natural" melting happened. But I could be wrong. -- Geoff The Sea Hawk at Wow Way d0t Com remove spaces and make the obvious substitutions to reply by mail When immigration is outlawed, only outlaws will immigrate. |
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Icing tape - lessons learned.
"Capt. Geoffrey Thorpe" The Sea Hawk at wow way d0t com wrote
1) I suspect (knowing nothing beyond what I heard) that the pilot failed to recognize the ice buildup untill control was lost. I ASSUME that she was in the soup at the time - so the lesson here is pay attention - it's cold, you are in the clouds, look out the window and watch for ice. Right? Always a good idea - use your flashlight at night to check. Also, keep in mind that the wings may be the least efficient ice collector on your particular airplane - the tail may be much more efficient (Mooney as one example) and be icing up nicely while you see almost nothing on the wing. So, while you're looking for ice be sure to take a glance back at the tail too, assuming you or your pax can see it. Tailplane stalls can be a huge bummer. BDS |
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Icing tape - lessons learned.
On Feb 6, 9:19 pm, "BDS" wrote:
Always a good idea - use your flashlight at night to check. Also, keep in mind that the wings may be the least efficient ice collector on your particular airplane - the tail may be much more efficient (Mooney as one example) and be icing up nicely while you see almost nothing on the wing. So, while you're looking for ice be sure to take a glance back at the tail too, assuming you or your pax can see it. Tailplane stalls can be a huge bummer. I thought the same thing. The tailplane ice would explain the "out of control" situation as opposed to an even set of airframe ice and its associated gradual decline in performance. If the main wings built up so much ice as to stall and lose control, it would strike me as unrecoverable or at least severe enough to not allow her to talk on the radio. Marco |
#9
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Icing tape - lessons learned.
"Marco Leon" wrote I thought the same thing. The tailplane ice would explain the "out of control" situation as opposed to an even set of airframe ice and its associated gradual decline in performance. If the main wings built up so much ice as to stall and lose control, it would strike me as unrecoverable or at least severe enough to not allow her to talk on the radio. I didn't listen to the tape but the descriptions that mentioned a sudden out of control dive sure sound like a tailplane stall to me. It can take a tremendous amount of force on the yoke to recover, and recovery technique is not intuitive because it is not the same as the technique(s) used for a normal wing stall. NASA has a nice tape on tailplane icing that is well worth watching. BDS |
#10
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Icing tape - lessons learned.
I think the lesson is stay aware of icing conditions, and if you must
absolutely fly in/near icing conditions - you better put the airframe into the instrument scan. Icing cannot be ignored, but that is precisely what this thread has hypothesized. First, the Caravan was flying in an area near icing. Strike One. Second, this thread has hypothesized that the pilot failed to use pitot heat, boots, and/or let the autopilot fly the plane into the stall. Strikes 2,3,4. Avoiding any one of these items likely would have precluded the incident. |
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