My 172N has the AirPlains SA2196CE STC for 2550 gross weight. The odd thing is that the flap lever detents are at about 15 and 25 degrees. For 10 degrees of flaps you have to move it half way to the first detent (to where it actually says 10 degrees). My AME says it looks like they used a CNC machine to cut the detents lower, probably when they were limiting the flap travel to 30 degrees for the STC. I can't quite figure out why increasing the detents would be necessary to limit flap travel.
I don't see anything in the flight manual supplement about this, and I've been happily flying around taking off with about 15 degrees of flap, as I never realised they had screwed around with the flap detents. The 172N POH says they should be at 10 and 20 degrees.
Anyway, I'm just curious if this is the normal installation procedure for the 30 degree flap limit. I don't have a copy of the documentation for this STC, but I see the installation instructions on AirPlains' website just discuss installing the tailcone stringers, but no mention of how to limit flap travel:
https://www.airplains.com/images/suppor ... %20gwi.pdf
172 flap detents at 15/25 instead of 10/20
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Re: 172 flap detents at 15/25 instead of 10/20
https://www.airplains.com/images/suppor ... signed.pdf
I found a link for a 172N model STC.
The flaps should only go as far as the flap jack-screw motor would take it.
So from factory it should only go as far as they set it (plus,minus a degree or 2).
Have to measured the flap travels to actually see what they are retracting at?
Ben
I found a link for a 172N model STC.
The flaps should only go as far as the flap jack-screw motor would take it.
So from factory it should only go as far as they set it (plus,minus a degree or 2).
Have to measured the flap travels to actually see what they are retracting at?
Ben
Re: 172 flap detents at 15/25 instead of 10/20
Yes, my AME was doing some work on them to fix a problem, and they are extending perfectly...at 10 degrees on the switch they are extending exactly 10 degrees, same with 20 and 30. The only issue is that the detents aren't at 10 and 20 as you can see in the photo:BGardner wrote: ↑Thu Jan 14, 2021 7:04 pm https://www.airplains.com/images/suppor ... signed.pdf
I found a link for a 172N model STC.
The flaps should only go as far as the flap jack-screw motor would take it.
So from factory it should only go as far as they set it (plus,minus a degree or 2).
Have to measured the flap travels to actually see what they are retracting at?
Ben
They are correctly limited to 30 degrees. I'm just curious about the detents.
Re: 172 flap detents at 15/25 instead of 10/20
Shouldn’t be a problem to ignore the detents, should it? Aren’t the original detents at 10 and 25? EDIT: you’re correct, 10 and 20 according to the POH.
Maybe you can adjust the switch position?
Maybe you can adjust the switch position?
DId you hear the one about the jurisprudence fetishist? He got off on a technicality.
Re: 172 flap detents at 15/25 instead of 10/20
The position of the flap control is of less importance than the position at which the flaps stop from transit. The detent in the photo shows where the bottom of the flap lever arm will touch, noting that the flap lever touches at the top at zero flap position. Hopefully, the flap position pointer (which actually controls the position at which the flap motor stops running), is set close to the position marks, if not, it should be adjusted. Correctly adjusted, it is what matters.
That said, while respecting the flight manual information for the plane, you'll probably find a 15 degree flap setting just fine for takeoff. Indeed, I deliberately set 15 flap on 100 series tricycle planes while taxiing, as that setting, combined with holding up elevator, has a pleasing effect in keeping the prop further from the ground.
That said, while respecting the flight manual information for the plane, you'll probably find a 15 degree flap setting just fine for takeoff. Indeed, I deliberately set 15 flap on 100 series tricycle planes while taxiing, as that setting, combined with holding up elevator, has a pleasing effect in keeping the prop further from the ground.
Re: 172 flap detents at 15/25 instead of 10/20
Moving the switch would mean the 10 degree / 20 degree markings would be wrong, and the limit would not be 30 degrees any more. If there was a fix, it would be to plug up some of the cutout so that the detent matches the 10 degree position. But that seems potentially problematic, difficult and/or expensive, so I'm just going to leave it as is and try to remember not to use the detents.
Re: 172 flap detents at 15/25 instead of 10/20
Yes, everything is working perfectly if you ignore the detents.PilotDAR wrote: ↑Fri Jan 15, 2021 7:51 am The position of the flap control is of less importance than the position at which the flaps stop from transit. The detent in the photo shows where the bottom of the flap lever arm will touch, noting that the flap lever touches at the top at zero flap position. Hopefully, the flap position pointer (which actually controls the position at which the flap motor stops running), is set close to the position marks, if not, it should be adjusted. Correctly adjusted, it is what matters.
Yes, it does work fine, although I think the POH might say something about more than 10 degrees being prohibited for takeoff.That said, while respecting the flight manual information for the plane, you'll probably find a 15 degree flap setting just fine for takeoff. Indeed, I deliberately set 15 flap on 100 series tricycle planes while taxiing, as that setting, combined with holding up elevator, has a pleasing effect in keeping the prop further from the ground.
Re: 172 flap detents at 15/25 instead of 10/20
It says “Flap settings if more than 10 degrees are not approved” for takeoff, but that’s perhaps different to “prohibited”.
Also it says that in a non approved section of the manual, so it’s advice, perhaps strong advice, but not perhaps a hanging offence if you work around it.
Also it says that in a non approved section of the manual, so it’s advice, perhaps strong advice, but not perhaps a hanging offence if you work around it.
DId you hear the one about the jurisprudence fetishist? He got off on a technicality.
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KissPlusOne
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Re: 172 flap detents at 15/25 instead of 10/20
Sometimes you need that extra 5 degrees of flaps to get you off of a particularly sticky surface.
Re: 172 flap detents at 15/25 instead of 10/20
Your flap lever and cutouts are correct!
The top of the flap lever indicates the flap selection/travel, so to get 10 degrees you select the flap lever to the bottom of the first cutout. The top of the lever will indicate 10 degrees flap and that should correspond with the actual flap angle. Same for 20 and 30 degrees.
The flap pointer should also indicate the the correct setting. However they are notorious for sticking or getting bent.
If the flap is not at the required setting then the flap lever cam located behind the dash on the flap lever is not rigged properly.
I believe there are up and full down limit switches on the flap screw jack also.
The top of the flap lever indicates the flap selection/travel, so to get 10 degrees you select the flap lever to the bottom of the first cutout. The top of the lever will indicate 10 degrees flap and that should correspond with the actual flap angle. Same for 20 and 30 degrees.
The flap pointer should also indicate the the correct setting. However they are notorious for sticking or getting bent.
If the flap is not at the required setting then the flap lever cam located behind the dash on the flap lever is not rigged properly.
I believe there are up and full down limit switches on the flap screw jack also.
Re: 172 flap detents at 15/25 instead of 10/20
Well if you look at the pic you can see there is a big difference in the distance between the 10 degree marker and 10 degree detent, vs the 20 degree marking and 20 degree detent. If you watch the flaps they travel a lot more between the first detent vs second detent. And the AME measured it and it is exactly correct when lever is at the specific markings, but he said the detents don't quite match up. Anyway, I'm not concerned. It's easy enough to pull it down to 10 degrees, or just accept 15 degrees at the detent which is no big deal.J31 wrote: ↑Wed Feb 24, 2021 5:51 pm Your flap lever and cutouts are correct!
The top of the flap lever indicates the flap selection/travel, so to get 10 degrees you select the flap lever to the bottom of the first cutout. The top of the lever will indicate 10 degrees flap and that should correspond with the actual flap angle. Same for 20 and 30 degrees.
The flap pointer should also indicate the the correct setting. However they are notorious for sticking or getting bent.
If the flap is not at the required setting then the flap lever cam located behind the dash on the flap lever is not rigged properly.
I believe there are up and full down limit switches on the flap screw jack also.
More of an issue is that the flaps aren't working at all now...the lever doesn't do anything, so he's going to have to look at it again. I miss the manual flaps of my old 172!
Re: 172 flap detents at 15/25 instead of 10/20
Sounds like you have a broken wire, miss rigged or failed micro switch. I would start with the limit switches on the flap motor in the wing.CpnCrunch wrote: ↑Wed Feb 24, 2021 6:33 pmWell if you look at the pic you can see there is a big difference in the distance between the 10 degree marker and 10 degree detent, vs the 20 degree marking and 20 degree detent. If you watch the flaps they travel a lot more between the first detent vs second detent. And the AME measured it and it is exactly correct when lever is at the specific markings, but he said the detents don't quite match up. Anyway, I'm not concerned. It's easy enough to pull it down to 10 degrees, or just accept 15 degrees at the detent which is no big deal.J31 wrote: ↑Wed Feb 24, 2021 5:51 pm Your flap lever and cutouts are correct!
The top of the flap lever indicates the flap selection/travel, so to get 10 degrees you select the flap lever to the bottom of the first cutout. The top of the lever will indicate 10 degrees flap and that should correspond with the actual flap angle. Same for 20 and 30 degrees.
The flap pointer should also indicate the the correct setting. However they are notorious for sticking or getting bent.
If the flap is not at the required setting then the flap lever cam located behind the dash on the flap lever is not rigged properly.
I believe there are up and full down limit switches on the flap screw jack also.
More of an issue is that the flaps aren't working at all now...the lever doesn't do anything, so he's going to have to look at it again. I miss the manual flaps of my old 172!
Don't go looking for problems that may not be there. Measure the flap deflection before deciding it is wrong, as optics can be deceptive.
The Cessna maintenance manual describes how to troubleshoot, measure and rig the flap system.
They are single slotted flowler flaps on the Cessna 172. For the first 10 degrees of flap the travel is more extension than deflection. To 20/30 degrees they now move more in deflection than extension.
To measure the flap deflection in degrees you set an inclinometer to 0 on the bottom of the flap with the flaps up. Then run the flaps to there respective 10, 20, 30 degree positions by positioning the flap lever in each respective slot, noting the degrees at each. There is a tolerance in the maintenance manual. If it does not meet the tolerance then you need to adjust the micro switches on the flap lever.
The flap lever slots become worn on high time aircraft however your airplane does not look worn.
Last edited by J31 on Sat Feb 27, 2021 4:32 pm, edited 1 time in total.
Re: 172 flap detents at 15/25 instead of 10/20
Yes, that may explain it. The AME did measure the deflection with an inclinometer and it was perfect. He did say that it doesn't match up with the detents and you need to use the 10/20/30 degree markings instead. I haven't measured it myself with an inclinometer, but I'll try that once it's all working again to see what exactly the deflection is at the first detent.J31 wrote: ↑Thu Feb 25, 2021 9:58 am
They are single slotted flowler flaps on the Cessna 172. For the first 10 degrees of flap the travel is more extension than deflection. To 20/30 degrees they now move more in deflection than extension.
To measure the flap deflection in degrees you set an inclinometer to 0 on the bottom of the flap with the flaps up. Then run the flaps to there respective 10, 20, 30 degree positions buy positioning the flap lever in each respective slot, noting the degrees at each. There is a tolerance in the maintenance manual. If it does not meet the tolerance then you need to adjust the micro switches on the flap lever.
The flap lever slots become worn on high time aircraft however your airplane does not look worn.
Re: 172 flap detents at 15/25 instead of 10/20
Your AME is wrong. You better get a current maintenance manual.
Re: 172 flap detents at 15/25 instead of 10/20
Looks like it's an indicator problem again. When I move the lever to first detent the flaps actually go to 27 degrees, and they go to 40 degrees at the 30 degree (max) detent. The indicator is showing much less flap than actual flap deflection. The original problem was the indicator was showing about 20 degrees with flaps up, so nothing was moving till you moved the lever past 20. AME fixed it and measured it with inclinometer, but seemingly more work is required.
Another plane I fly has a similar indicator issue (indicator never reads less than 10 degrees with flaps up), but it has the up/down switch without detents so it's not really an issue.
Another plane I fly has a similar indicator issue (indicator never reads less than 10 degrees with flaps up), but it has the up/down switch without detents so it's not really an issue.
Re: 172 flap detents at 15/25 instead of 10/20
Just a quick update: AME fixed this and the flaps (and detents) are working perfectly now. Just one of those things that it took a couple of goes to completely iron out the problem. (He did use an inclinometer after the first fix, but for whatever reason it didn't stay fixed). It's been working perfectly for a few months now, but I now have a healthy distrust of Cessna electric flaps.
