cessna 150 flap switch

[Sleepingsquirrel]

Around 1966 or 1967 the flap switch was changed. I have a G model where the flap switch is placed in the down position (switch must be returned to neutral) or the flaps extend fully. You must hold the flap switch in up positon to get the flaps up (it is spring loaded to neutral from the up positon) Is this correct or has someone mistakenly turned the switch upside down?


Pilot Friend info
"C-150 flaps have evolved from the Piper like Johnson bar through various flap switches and indent levers. Be careful, some switches work 'backwards'. The later models of the C-150 have electric flaps with indicators marked in 10 degrees to 40 degrees. There is a flap-shaped switch, which applies power to an electric motor and a worm gear to the flap-actuating rod. Extension takes about nine seconds and airstream assisted retraction takes about five seconds. Any count system used to move flaps should be figured accordingly. The flap indicator works on a cable + pulley system which has variations in accuracy. Different year models of the C-150 and all other models have different modes of switch operation. Be sure to check method of operation before flight and during checkouts."



Thanks!

 

[flyingron]

All the ones I've flown you must HOLD down to extend but it will lock in the up / retract position. THen they switched it on the 152 to the "stair step" set it where you want it type lever.

 

[Dan Thomas]

Around 1966 or 1967 the flap switch was changed. I have a G model where the flap switch is placed in the down position (switch must be returned to neutral) or the flaps extend fully. You must hold the flap switch in up positon to get the flaps up (it is spring loaded to neutral from the up positon) Is this correct or has someone mistakenly turned the switch upside down?

It's either installed upside-down, or one return spring in the switch is broken. The earliest switches were sprung from both Up and Down to the Off (center) position, and there were no limit switches on the flap actuator. A slip clutch on the jackscrew prevented damage if the motor continued to run after the flaps were all the way up or down.

If yours has a switch that was changed in '66 or '67, it's an old airplane that should have the switch sprung to Off from either position.

Newer models had the spring from Down to Off only, and limit switches on the actuator.

Dan

 

[tinerj]

I flew one that you had to pull back to middle to turn off down flaps. Once pushed down, you could remove your hand and it stayed down and would go all the way to 40 degrees flaps.

The next time I flew in a different C150, I pulled it up to turn it off, but it had sprung back to neutral and when I pulled it up, it went to up position to raise the flaps.
The CFI did not believe me at all when I described why I had to pull up on it. He insisted no airplane in existence would stay down -- it had to be held down.

Apparently his only experience is the one that they rented, because in the seven or so that I've rented, the flap activators work in a bunch of different ways.

 

[Pilawt]

Around 1966 or 1967 the flap switch was changed. I have a G model where the flap switch is placed in the down position (switch must be returned to neutral) or the flaps extend fully. You must hold the flap switch in up positon to get the flaps up (it is spring loaded to neutral from the up positon) Is this correct or has someone mistakenly turned the switch upside down?

The '66 (150F) and '67 (150G) had a toggle switch that was spring-loaded in both directions. On the 150F it was just a bare toggle switch, they added the flap-shaped handle on the '67 150G.

For 1968 (150H) the switch was spring-loaded down, and a detent held it in the up position. That was the system used until the last year of C-150 production, when the 1977 150M went to the pre-select switch, which was carried over to the C-152.

So it sounds like you have a '68-'76 style switch, wired and installed upside-down.

 

[Dan Thomas]

The CFI did not believe me at all when I described why I had to pull up on it. He insisted no airplane in existence would stay down -- it had to be held down.

A classic symptom of a broken centering spring. Believe me, guys, these springs break regularly. They're inside the switch and since that switch is worked quite a bit during approach and after landing, they don't last more than a very few thousand hours at the most. We had two 150s and four older 172s, and all of them experienced broken flap switch springs several times over the years.

A broken down-to-center spring can be dangerous, especially in the 150. You hold the switch down to get 10° flap, maybe, and then release it, expecting the flaps to stop. They continue downward, and in high DA conditions and with carb heat on you might find yourself descending despite max power. A broken airplane and injured or dead occupants just because the airplane wasn't inspected properly by anyone who knew what to look for.

Dan

 

[Tom-D]

The 150 flap switch part number is very serial number specific, when you order from your Cessna dealer you will be required to give the aircraft serial number.

plus there are upgrades to this switch.

 

[flyingron]

A broken down-to-center spring can be dangerous, especially in the 150. You hold the switch down to get 10° flap, maybe, and then release it, expecting the flaps to stop. They continue downward, and in high DA conditions and with carb heat on you might find yourself descending despite max power. A broken airplane and injured or dead occupants just because the airplane wasn't inspected properly by anyone who knew what to look for.

Dan

I had the reverse problem one time. I had lowered the flaps and took my finger off the switch, but the spring must have shot it past center into the stuck "UP" position. It took me a bit to figure out why I was suddenly going faster on short final.