Stall Warning Location on 77 P's

[Dave Underwood]

Does anyone know why Cessna moved the stall warning sensor on the leading edge, left wing, further outboard in 1977 at about serial number 260 G model P-series?

This has major implications with the de-ice boots as I have just found out. The Manual is wrong for my serial number as it specifies -05, where it should be -01. The replacement boots supplied were for a stall warner further outboard, but mine is inboard.

Bad news as it will now be a question of who made the error.

This is a word of warning for anyone contemplating de-ice boot replacement, with an aircraft in that serial number range, check the location of the stall unit. The manual is wrong on my aircraft which is Reims serial number 19.

Goodrich says the only difference between the -01 and the -05 is the pad location for the stall warning being moved outboard.

Depending on what happens this week, I may have a left hand wing de-ice boot for a late model P, serial number above 260 or so, for sale. That is with the stall warner further outboard. All paperwork supplied and it was built by Goodrich and delivered Sept. Any interest, please let me know.

Regards - Dave

[Bob Cook]

Dave

Mine is outboard. s/n 170.
Probably due to it being influence by the prop or perhaps being hit by ice being slung from the front prop. This is only an educated (lose term) guess.

Ouch.........

bob

[Dave Underwood]

Bob, could I ask you to measure the vane location on your plane just for comparison the next time you are out. If your's is outboard at about 120" (305 cm) from the fuselage, that must have been done as part of the Riley mods as the Parts Cat. says it happened at c/n 260.

My plane is approximately c/n 266 in late 1977 and although the location should be about 120", it is located at about 80" (198 cm) from the fuselage.

Does anyone else with a later model P care to measure the location of the stall vane and we can compare notes.

The DA (Design Authority) at Reims is looking at the drawings and admits something is wrong, certainly inconsistant. My hope is he will say to relocate it to 120" and provide the appropriate drawings and any required authority. (But then again I am an overly optimistic person when it comes to these sorts of things.)

As a note to anyone replacing your de-ice boots, take care if you are ordering them and make sure Goodrich understands which part number you need for your plane as there are inconsistancies.

Regards - Dave Underwood

[Bob Cook]

Dave

I may have spoken too soon. I will measure and get back to you. Based on your measurements mine appears to be in closer than yours (guessing). I would say mine is about one foot outboard of the strut.

Bob

[Dave Underwood]

.Epilogue: Well my story on this has gone from simple (replace boots) to complex (the stall warning pad is in the wrong place) then back to simple (move the stall warning vane to match the pad location).

How did this happen you might ask? Well Cessna allowed a deviation on the build on my plane to use a middle wing skin from the slightly earlier models (presumably they had an extra one that they wanted to make use of). This deviation was actually documented, but the information has stayed in the drawing cabinets ever since.

The stall vane can be in any one of three positions in the middle section of the leading edge L/H wing, so Cessna will issue a repair recommendation to allow the vane to be moved to where is should be and it can be moved under a Form 337.

Good news as that is cheaper than a new boot as there was no credit to be had and there would have been the delay to have one built. The plane now is more consistent with the parts catalogue as well.

Thanks to my FAA friends for the positive view of the change and to Scott and Samir at Cessna and Tequi Kazi at Reims for for their assistance.

For learning outcomes: if you are going to change your de-ice boot, make sure you talk with Goodrich and know which location your stall warning vane is located so you get the part you need first time.

Regards – Dave Underwood

[Paul Sharp]

Good to hear that one came out OK on this, especially since the cost of the boot would have been absorbed as a loss.