Mooney down @ Baker City, OR

[Mooney in Oz]

55 minutes ago, Andy95W said:

I wonder, in Victor's example above, if the stick pusher was over ridden or inoperative, and if investigators could tell by the FDR?

Although I know the crew this happened to from a previous life, I have not discussed the incident with either of them.  However, I know the stick pusher was not overridden and I am sure it was not inoperative.  I cannot remember why it did not work. The incident took them both by surprise with the FO freezing and the Captain luckily swinging into action as the wing dropped.  The SAAB dropped about 1,100 feet AGL.

Absolutely terrifying.

More info -

@Andy95WI just did a search for the incident and the investigation revealed the SAAB stalled before the stick shaker was activated due to ice accumulation, therefore the crew did not receive any warning of the impending stall.

Sorry Andy, I should have checked first.

It does makes me wonder whether our Mooneys would do the same, stall without stall warning activation due to too much ice accumulation.

[Hank]

1 hour ago, Mooney in Oz said:

It does makes me wonder whether our Mooneys would do the same, stall without stall warning activation due to too much ice accumulation.

I would be surprised if this did not happen! The stall warning tab is set to open at a specific angle of attack, but as ice loads the plane unevenly the stall speed increases in an unknown manner, so the angle of attack will be lower. What is the tolerance on tab opening angle of attack? I have no idea . . . .

[StevenL757]

On 8/21/2018 at 3:41 PM, Hank said:

"Nothing is foolproof to a sufficiently talented fool."

No matter how much idiotproofing you do, the breed of idiots continues to devolve to lower and lower levels of idiocy . . . . . .

Amen.

[Marcopolo]

22 hours ago, Hank said:

I would be surprised if this did not happen! The stall warning tab is set to open at a specific angle of attack, but as ice loads the plane unevenly the stall speed increases in an unknown manner, so the angle of attack will be lower. What is the tolerance on tab opening angle of attack? I have no idea . . . .

Assuming the Stall Warning Tab is not iced also!  If heated it needs to be turned on, if not heated (like mine) and iced over, its clueless to AoA.

 

Ron

[exM20K]

42 minutes ago, Marcopolo said:

Assuming the Stall Warning Tab is not iced also!  If heated it needs to be turned on, if not heated (like mine) and iced over, its clueless to AoA.

 

Ron

The unheated stall warning vane *will* accumulate ice between the top of the vane and the housing.  It will look like a nice little marble.

Edited August 24, 2018 by exM20K

[carusoam]

On 8/23/2018 at 10:55 AM, Mooney in Oz said:

Although I know the crew this happened to from a previous life, I have not discussed the incident with either of them.  However, I know the stick pusher was not overridden and I am sure it was not inoperative.  I cannot remember why it did not work. The incident took them both by surprise with the FO freezing and the Captain luckily swinging into action as the wing dropped.  The SAAB dropped about 1,100 feet AGL.

Absolutely terrifying.

More info -

@Andy95WI just did a search for the incident and the investigation revealed the SAAB stalled before the stick shaker was activated due to ice accumulation, therefore the crew did not receive any warning of the impending stall.

Sorry Andy, I should have checked first.

It does makes me wonder whether our Mooneys would do the same, stall without stall warning activation due to too much ice accumulation.

One added part of Fiki instrumentation is a heated stall warning to go with the heated pitot tube...

Check to see if you have a heated stall warning device and if it is operational...

A heated AOAi would be better than an unheated one... on those few days where flying in icing conditions occurs....

Is this what you had in mind?

Best regards,

-a-

[Mooney in Oz]

9 hours ago, carusoam said:

A heated AOAi would be better than an unheated one... on those few days where flying in icing conditions occurs....

I fully agree Anthony, although I have not researched this to see if heated AOA probes for GA is available.

The Aspen AOA system does not use  any external hardware, deriving data from it's ADC and AHARS therefore negating the need for anything heated.  

I never seriously thought about an AOAi with the heating issue until this discussion. It is making me seriously consider having the software installed on my EFD or possible soon to be upgraded Max EFD.  

[kpaul]

10 minutes ago, Mooney in Oz said:

I fully agree Anthony, although I have not researched this to see if heated AOA probes for GA is available.

The Aspen AOA system does not use  any external hardware, deriving data from it's ADC and AHARS therefore negating the need for anything heated.

Heating the AOA won't help unless the plane is also FIKI.  The stalling AOA of a wing is assuming the wing is not contaminated.  If its covered with ice the airfoil has effectively changed, therefore changing the AOA in which it would stall. The Aspen AOA would not help with a contaminated wing either.

[Mooney in Oz]

9 minutes ago, kpaul said:

The Aspen AOA would not help with a contaminated wing either.

Thanks Kevin.  Shows how much I know and don't know.

[carusoam]

Let’s consider for a moment...

• the wing is carrying a fair amount of ice on it...
• it’s stall speed and associated AOA is no longer known...
• you have a stall warning device that is heated...
• And an AOAi that is heated and still 100% operational...
• You have become a test pilot by your own hand...

 

• You will be able to make judgements about your change of AOA, as you increase the AOA in the most controlled fashion...
• If you start to feel the buffet, Lower the nose while you note the IAS and the last seen data from the AOAi....
• you have accidently defined the current edge of the new flight envelope, a place to not go back to until 3’ above the longest runway...

Ice is a serious matter.  The limiting AOA with an iced wing is going to be different.  But it would be much better to be very informed about how things are going even when you don’t know where the limits are...  making small adjustments is better when you know how small the adjustments are...  add small control inputs + note the change on the instruments... a two pronged approach...

As far as parts go...

Mooney supplies a heated stall indicator for The FIkI systems... so it’s Mooney parts to be sought...

Even if I didn’t have a full fiki system, a partial system would have benefits...  like a heated prop.

 

when gathering ice you have several challenges building at the same time...

1) Loss of lift... air flow separation caused by the change of the wing shape (get them de-iced)

2) Loss Of instrumentation... frozen pitot, Static, stall warning, and/or AOAi... (get them heated)

3) increased weight needed to be supported... ice is heavy as it attaches all over the plane... (get out of dodge quickly)

4) Loss of thrust, as ice disturbs the shape of the prop airfoil... hard to maintain level flight with out lots of power... (chemical sprayed or heated) a second problem occurs with uneven loss of ice from the prop... that causes huge vibrations and probably a need to pull the power...

Discussing ice in the middle of the summer is a whole lot more comfortable...

PP thoughts only, only have a minimal anti-ice system on my plane... not a CFI.

Best regards,

-a-