I Was wondering if anyone out there knows how to check the wing incidence on a 1959 Cessna 182?

My 182 doesn't seem to make the numbers in the manual. At least I'm pretty sure it doesn't. The book says that at 2450 RPM and 23 inches, The airplane should cruise at 158 mph TAS at 2500ft MSL. I did a test at 2000 ft. on a 70ish degree day and the most I saw indicated was 144 mph at those settings. I suppose that the old prop could be less efficient than when it was new, and the old engine might not be putting out like it used to, however, a conversation I had with a friend made me think it might be the incidence. My friend is an avid skydiver, and a Private Pilot, and has a bunch of time in a 182 jump plane. He said one of the common modifications to jump planes was to increase the wing incidence for better climb performance. My plane had, one time been converted to a jump plane, but there is no record of it ever being used as one, and was converted back. My theory is that the incidence may have been increased when converted, but they forgot decrease it when they converted it back. One of the reasons I don't think it is the engine or the prop, is that it climbs very well. At least as well as stated in the book.

I know that the incidence is adjustable on the rear spar, so there must be a way of determining what the incidence is.

Thanks

Refer to the Cessna 182 Series maintenance manual for rigging the wing and fuselage establishing level. http://hhh.gavilan.edu/hspenner/iLearnI ... Manual.pdf

Incidence normally would be relative to the wing's airfoil chord line and fuselage level line. Tough to find the chord line from external skin.

There's some info that Cessna used +1.5* +- wing root incidence on 172's and maybe others. However in your case if you're interested in current wing angles an easier method would be to obtain a digital level and measure the value at some arbitrary station near the wing root. Aircraft angle on the ground isn't critical. Mark and place the level (longer is probably better) on the bottom of the wing in front of the flap cove. It's flatter there than further forward. Note the value. Then do the same for the other wing at the same relative location. Now crank the rear spar eccentric adjusters to move the wing full up and full down. Note the differences and pick a value between them. Rear wing up for speed; down for lift.

Unless someone has a different opinion I'd assume Cessna initially set the two adjusting cams mid-way in their rotation. They or others may have moved them in the meantime to correct for wing heaviness or lift or speed. Check and see what you have.

Also note the relative position of the inboard flaps to the adjacent fairing riveted to the fuselage. Some are up and some down. Same for outboard flaps and aileron tailing edge rigging. They probably should line up fairly well.

Gary

I cannot tell you how many aircraft we got at the repair station that where improperly rigged. Then there is the really simple thing that was a common issue, the Turn and Bank put in improperly. Check the level of your aircraft, usually by laying a level across your seat tracks and getting the wings perfectly level. Then adjust your Turn and Bank so the ball is centered. This result of some Gomer just putting the T&B in without leveling the aircraft tends to have a rather big effect on the speed of your aircraft, since your essentially flying around in a side slip.

After that, check the full rig on flaps and ailerons, the procedure is set out in the maintenance manual. Then there is the unfortunate, "your plane is just bent." It was rather shocking to see how bent they could be when your in 4 plane formation and they all are just a bit off.

Checking the wing eccentric settings is worth doing, but there are literally dozens of other sources of drag that will slow an old airplane down. Also note that these kinds of data from a manufacturer were derived using a brand new, perfectly rigged airframe......to provide bragging rights and induce sales.

Beechcraft was one of the few manufacturers whose performance data was nearly always conservative.....a great sales strategy, in my mind. New owner is asked by another prospective customer about performance. New owners says his plane outperforms factory specs....happy customer.

With Cessna, that 182 brand spanking new may not have met factory specs.

Things like control surface rigging can make a huge difference. As Gary noted, those eccentrics may be rigged different from each other to compensate for something else = more drag. Etc.

MTV

What was the pressure during your test? Looks like you're comparing TAS from the book to IAS during your flight. If you do a TAS calc those numbers will be much closer.

Skeletool wrote:….My 182 doesn't seem to make the numbers in the manual. At least I'm pretty sure it doesn't. The book says that at 2450 RPM and 23 inches, The airplane should cruise at 158 mph TAS at 2500ft MSL. I did a test at 2000 ft. on a 70ish degree day and the most I saw indicated was 144 mph at those settings.......

First off, is your airspeed indicator accurate?
Go fly on a calm wind day & make some runs using different headings & check airspeed vs GPS ground speed.
Secondly, there's airspeed and then there's airspeed: indicated airspeed, true airspeed, and calibrated airspeed.
Your factory numbers are in TAS, you're using IAS.
Thirdly, 23" / 2450 getting you 158 at 2500' sounds optimistic--
of course, I'm used to IAS figures not TAS so maybe it is realistic.

I will second what others have said-- check the rigging.
I'd suggest having someone familiar with this re-rig it from scratch.
Bigrenna just posted the other day that he properly re-rigged his C180 and gained 11 mph.

Thanks for the great replies! To answer some questions:

I have checked the airspeed indicator vs. the GPS and the IA is right there with the GPS on a calm day.

I didn't write down what the temperature and pressure was when I did it, but I played around with a TAS calculator, and I tried pressure from 28" to 31" and it didn't make a big enough difference for my 14 mph discrepency.

dogpilot,

Love the idea about the T&B! I don't think I would have ever thought of that!
The airframe only has about 2800 hours on it and no damage history, so hopefully it's not bent.
It does fly pretty strainght hands off at idle.

Thanks PA1195 for the info on checking the incidence. I have a digital level, so I'll have a look this weekend.

I agree with everyone that there are numerous sources of drag. I would like to find out if this is a culprit. If not I'll move on to the next thing. I was curiuios if there was a datum to measure the incidence from and what the spec should be at the factory.

My partner and I removed all the in-necessary instruments and related antennas, so we're down to a Com antenna, low profile Garmin GPS antenna, ELT, stubby transponder antenna, and a blade antenna for the ADSB IN. We also got the weight to within 35 or 40 lbs of what it was when it was new.

I'll keep you posted what I find out this weekend.

Thanks again!

mtv wrote:Also note that these kinds of data from a manufacturer were derived using a brand new, perfectly rigged airframe......to provide bragging rights and induce sales.

MTV

On the other hand....
Our 68’ Skylane meets all the book numbers. Don’t ask me how. Despite a stock McCauley prop, mid time engine, one flap slightly lower than the fuselage fairing, both ailerons centered with the trailing edge of the flap but not streamlined at the wing tips, and a fuselage bristling with seven antennas, and no speed mods.
Every couple of years we fly the same triangular corse that takes almost exactly one hour. The last time we did it we had just finished some work on the fuel system. Since the plane was refuled with a known quantity, w e used the opportunity to get better numbers for fuel burn. (Also meet book numbers to a T)
For years I have looked at the flight control on our bird with disgust. But the tensions, travels and numbers are such that I’m afraid to touch them.

It's not an easy task to confirm rigging but it can be rewarding. There's the book data above for wings (adjusted by two eccentrics in each wing), flaps, and ailerons adjusted by various links and controls to set certified travel limits.

But before that it helps to fly around and note the position of the various controls in level flight and wing relative to the horizon. Trims set this way and that, yoke alignment versus aileron position, and flap position relative to the ailerons. Drop a little flaps..does the plane roll one way or another? The T&B ball panel adjustment is a good one. Pitot and static lines for leakage are something we can do ourselves. A rudder trimmed far off center to center the ball may indicate a correction for wing maladjustment. Simple things to note and record for later.

Then on the ground I'd have a look at the flaps, ailerons, and wing incidence eccentrics on the rear spar. For the eccentric bushings just to note their current position and between wings. Might give some indication if they've been altered. A level on the bottom of the wings may detect any difference between them but probably not much as to true incidence. If the controls (flaps, ailerons) are unaligned or in an odd position in flight try to relate that to the incidence adjustments and on ground alignment...wing heavy or light for example. Flight loads can stretch loose control cables and create issues. Even a tailwheel cranked L or R in flight can affect trim and airspeed.

There's some basic things to do and I hope it gets better.

Gary

Skeletool wrote:Thanks for the great replies! To answer some questions:

I have checked the airspeed indicator vs. the GPS and the IA is right there with the GPS on a calm day.

I didn't write down what the temperature and pressure was when I did it, but I played around with a TAS calculator, and I tried pressure from 28" to 31" and it didn't make a big enough difference for my 14 mph discrepency.

dogpilot,

Love the idea about the T&B! I don't think I would have ever thought of that!
The airframe only has about 2800 hours on it and no damage history, so hopefully it's not bent.
It does fly pretty strainght hands off at idle.

Thanks PA1195 for the info on checking the incidence. I have a digital level, so I'll have a look this weekend.

I agree with everyone that there are numerous sources of drag. I would like to find out if this is a culprit. If not I'll move on to the next thing. I was curiuios if there was a datum to measure the incidence from and what the spec should be at the factory.

My partner and I removed all the in-necessary instruments and related antennas, so we're down to a Com antenna, low profile Garmin GPS antenna, ELT, stubby transponder antenna, and a blade antenna for the ADSB IN. We also got the weight to within 35 or 40 lbs of what it was when it was new.

I'll keep you posted what I find out this weekend.

Thanks again!

Borrow a tach checker from a mechanic or friend. Take it with you when you fly and verify that your tachometer is accurate. Most mechanical tachs are off, some by quite a bit.

If that's the case, you'll be running a different power setting than the factory used for their data, even though your tach SAYS you're running the same power. If your tach reads high, that could explain at least part of the discrepancy you're seeing. In that case, you'd be running less power than the factory used to develop data.

MTV

I've just put the wings/tail/flight controls on our U206F project. So I was obviously keen to read all I could about the rigging. I asked a question from the CPA as to what is the default position for the cams on the aft wing attach bolt. Here is the reply from Paul New, Tennessee Aircraft main man.

"When we install wings we align the eccentrics so that both bolts are at the top. In this way, if any adjustment needs to be made it's only on one side and only in one direction. Always rotate the eccentrics so that the bolt moves away from the cabin. This will keep the flaps from contacting the cabin fairings."

This is the way I have done it. I am also getting a technician who has done the CPA rigging course and travels the world rigging Cessna's to come and set this up by the book. I am going to get it close and let him refine it. The difference in speed in one rigged with a high angle of incidence and low angle of incidence is notable. Fast and less float in the flare would suit me just fine.

Status Update: Problem solved.
Root Cause : I'm an idiot.

So I went through and checked a bunch of the things that were suggested, and in the end, everything looked good. So I went up and did another speed run to see if I could figure out why my speeds were slower than the book. I took off and leveled off at 1500 MSL, and noted that the OAT was 50 F and the barometric pressure was 29.92. I set the RPM to 2450 and the MP to 23", and trimmed out the airplane. I was still indicating in the 140's. But then it occurred to me that maybe there was more parallax on my view angle of the gauges, than I thought. Once I set the RPM and MP looking at the gauges straight on, I was indicating 154 mph. This turns out to be 157 mph TAS, and the book says I should see 158 mph. So apparently all is good..... except for the part about me being an idiot......

Thanks for your help everyone!

Good news! And, thanks for reporting back. It's always nice to hear "The rest of the story".

MTV

Just did a quick ck and 144 IAS at 2000' 71degF is 150TAS

Thanks for posting the rest of the story.

I have a 182 wing incidence question of my own but I don't think it will be solved as easily as by admitting I'm an idiot;-)

I've had our '63 182 (Sportsman/Wing-ex) in for wing paint and flap reskinning. I knew they had to remove the wings to fit them in their small paint booth but I didn't realize they were going to disassemble everything. Wing extensions are off, flaps off, ailerons off. Same with the tail feathers.

Your thread and a comment from my mechanic today has me wondering about how to check my own wing alignment after they are re-installed. When I told him I'd probably be able to pick up the plane Friday he asked me to budget a couple hours for one or two test flights in case we need to adjust the wings or fiddle with the gear (my gear wouldn't come down last flight until I used the hand pump).

I'm smart enough to know I have a problem when the gear won't come down but how the heck am I supposed to know if my wings need adjustment? I'm on amphibs and the plane is heavily modified anyway, so book values don't mean much. The wings were peeling like crazy and rougher than sandpaper in many areas, so with slick new paint I expect to see higher speeds than before, but I don't know how much to expect.

If she doesn't fly straight or level that will be an obvious clue something needs to be adjusted, but is there something else I should be looking for?