Why the squat switch on the stall horn of the PA44?

SkiHigh2002

SkiHigh2002

New Member
I'm reading through the Seminole POH today and I noticed the paragraph that says the squat switch is connected to the stall warning horn so that the stall warning will be deactivated on the ground. Why is this? Why would the stall horn not need to work on the ground? My guess is that it has something to do with the stall tabs and aerodynamics. Any takers?
 
What if it was windy and the wind kept clickin the lil stall tab while you were taxiing around? Would that be fun? No.... ;) So they put in the squat switch. That's how it was explained to me at least, and I couldn't think of any other reason why besides that.
 
Does it really matter? If you can't tell the aircraft is about to stall when you get to the buffet you've been trained very, very, very poorly.
 
Yep. Because when the Seminole stalls, it feels like the wings are about to fall off from the buffet.
 
The funny thing is that not all twins are set up like that. When I was a ramper at STL, I pressed up the stall warning horn on a Jetstream 32 thinking that nothing would happen. WRONG! The captain of the mighty J32 comes out and he is pissed. He very slowly explains to me that the stall warning horn is a very sophisticated piece of equipment :D
 
Foxcow said:
I pressed up the stall warning horn on a Jetstream 32 thinking that nothing would happen. WRONG! He very slowly explains to me that the stall warning horn is a very sophisticated piece of equipment :D
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The lift transducer stall warning setup on the Jetstream is a bit more complicated than what you would find on a Seminole. It really is best that it not be messed with too much on the ground.

I have found that leaving the heat on momentarily when known jokers are around is sometimes an effective deterrent.
 
Actually, the seminole has squat switches on the stall warning horns because the propwash from the left engine would cause them to engage off and on driving you absolutely nuts.

That's what I was told at least. Makes sense, they dont look any different than the ones on the warrior(except that there are two) and those aren't bothered by anything for the most part.
 
Ok the last reply is very interesting to me. Aerodynamically what is happening here? Does it have something to do with the propwash and the relative wind?

Sorry, I'm just trying to get to the bottom of this.
 
The explanation I always rec'd - even from Piper MX people - is the stall horn is turned off so you can test it to see if its working. If you flip it up and hear something it isnt functioning correctly. There should be no sound when its actuated.
 
I was always told it was a prop wash thing, not a wind thing, or every airplane would have that (semis aren't the only airplane that taxis in the wind). The Baron's stall horn works on the ground. If you look at where the lift detector is in relation to the prop it is much farther out (relatively) than the semionles two switches are.

I could be way off too, never got an official answer from anyone who would know, ie Piper.
 
Berkut said:
The lift transducer stall warning setup on the Jetstream is a bit more complicated than what you would find on a Seminole. It really is best that it not be messed with too much on the ground.

I have found that leaving the heat on momentarily when known jokers are around is sometimes an effective deterrent.
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I stand corrected. Maybe I should not have rolled my eyes when I apologized.
 
Dugie8 said:
I was always told it was a prop wash thing, not a wind thing, or every airplane would have that (semis aren't the only airplane that taxis in the wind). The Baron's stall horn works on the ground. If you look at where the lift detector is in relation to the prop it is much farther out (relatively) than the semionles two switches are.

I could be way off too, never got an official answer from anyone who would know, ie Piper.
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I'm pretty sure you and I are right. I'm not sure where I saw it printed, could have been in a maintenance manual that Al Johnson showed are class. You went to UND right?

I am however not sure if its propwash alone, or if it has something to do with the way the relative wind affects the propwash. I know it's something with propwash though.
 
SkiHigh2002 said:
Ok the last reply is very interesting to me. Aerodynamically what is happening here? Does it have something to do with the propwash and the relative wind?

Sorry, I'm just trying to get to the bottom of this.
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As far as I know, its just the turbulant air coming from the prop, interacting with the wing as well as hitting the stall warning vanes, causing them to move.
 
After touchdown, if you hold the nose off, with the right combination of wind, propwash and nose-high attitude, you might get the stall warning horn. Ever get that in a 152/172 softfield landing? So the Seminole is designed not to scare your pax with an "emergency" horn blaring on the landing roll.
 
As I recall the Seminole's outermost stall tab is the one that is active when the flaps are set to 0 or 10 degrees, the furthest from any propwash. Who taxis around with flaps in?

Mike
 
nosehair said:
After touchdown, if you hold the nose off, with the right combination of wind, propwash and nose-high attitude, you might get the stall warning horn. Ever get that in a 152/172 softfield landing? So the Seminole is designed not to scare your pax with an "emergency" horn blaring on the landing roll.
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Seminole noses' plummet to the ground after the mains land, it's kind of hard to keep it up
 
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