Avionics shop in midwest????/avionics access panel

Pat Rolfes · #1 11-14-02, 11:04 AM

Does anyone have a suggestion for a decent avionics shop in the midwest area? Specifically one which has some expertise with ARC 400A autopilot.

Any help would be appreciated.

Bob Cook · #2 11-14-02, 11:50 AM

Pat

What is the problem with it ? Then perhaps I can make some suggestions as to repair or service centre.
Does it have the IFCS ?

Bob

Pat Rolfes · #3 11-15-02, 11:19 AM

What is IFCS?

I think I have mentioned to you before that I have been using KCAC in Olathe. My problem is that the FAA just stole the main guy out of that shop and I don't think the remaining crew have a clue about this system. I suspect my problems would be easily found at the right shop.

I will try and describe my problems but forgive me in advance as I have extremely limitted understanding of electronics and this system.

I have been having intemittent problems (gradually getting worse) with the alt functions. It started out where I would suddenly notice my alt creeping up or down. To correct I would need to disengage system (just disengaging alt switch and rollong pitch wheel would not correct), position the yolk to straight and level flight and then re-ingage.

The next indication that things were getting worse was when I would extend landing gear I would lose alt (I once let it go as much as 1500 fpm before taking MANUAL corrective action).

The last symptom just happened on latest flight. Porposing (sp?)to the point of getting to my stomach (maybe as much as 75 ft up and down and up and down...) Kept it going for a while to see if it would self correct but couldn't take it anymore.

Thoughout, when these problems arise, the units pitch control wheel is completely non functional. I try and disengage alt hold button and turn pitch wheel (on system) to correct but it just rolls freely with no actual input to elevators. Also,during normal times, when the system corrects alt, you can physically see the pitch wheel turn in conjuction. During malfunction it doesn't move at all even tho elevator is clearly being moved by the system.

Sorry about the rample but don't have ability to make more concise.

Jim Rainer · #4 11-15-02, 07:59 PM

Try Auto Pilots Central, Tulsa. www.autopilotscentral.com. THE experts on 400 a/p. Also all avionics.

Bob Cook · #5 11-15-02, 10:08 PM

The IFCS = integrated flight control system. There is a control with 9 buttons. I assume your head has three horizontal switches on right. what year is the AC?

You can test the AP on the ground first without going in the air. If you centre control colomn the elevator TRIM should move up and down against tension on the elevator (pull in and out). You may need to assist the control column on this test but when engaged at approx cruise position of yoke then moving the evevator climb/decent wheel from its detent the elevator should move accordingly. As I said you may need to assist slightly due to elevator load in static position. If these work your servo(s) are working. In the none alt hold mode you should be able to hold approx level flight with electric trim then be able to move out of detent and adjust climb or decent rate (while stillon the ground).

You were not clear about the horiz control. Could you turn left and right manually while the alt was not functioning? IF NOT then sounds like the power supply in the computer, which is located over the pilots side rear seat in the headliner. It may becoming intermittent due to heat or based on the time it has been on. A fluctuating power supply will cause symptoms you described.

There is a good shop at Lunkin (KLUK) in Cincinnati. Alternative is to remove the computer and send for a bench test based on info above. You can email me directly if you have more questions. Autopilotcentral is fine but recommend you take the AC for repair rather than sending components. They are priceless <G> if you ever lose them which you do not want to do.....

Bob

Pete Somers · #6 12-01-02, 08:51 AM

THE PITCH SERVO IS U/S, A/C IS TRYING TO FLY ON THE TRIM SERVO BUT CANNOT DUE TO THE LOW SPEED OF THE TRIM.

PETE

WebMaster · #7 12-06-02, 06:29 PM

you know that covers a lot of territory. Where abouts in the midwest are you. Mayday, in GRR, takes care of a lot of Cessnas, and are attached (rent hangar space from) to Northern Air, a cessna dealer.

Pat Rolfes · #8 12-09-02, 10:34 AM

Thanks to all for the help.

It seems I now have a VFR autopilot. I have flown 8 legs in the last 3 wks (all in clear weather) and it flew just fine. I tried Bob's suggestions in the hanger and it worked perfectly. Of coarse, the only time it has been failing is when I actually need it (low ceilings, clouds, ice, etc.).

I seriously am wondering if I might be getting some moisture in the unit in bad weather (some sort of leak around the computer area). I pulled the ceiling liner to see if there was anything obvious (there was not). Anyway- my next coarse of action is to test for leaks.

WebMaster · #9 12-11-02, 09:57 AM

Water can be a bad thing. is yours a P-model? The un-P's are notorious for leaking around the avionics access panel.

Don Hickman · #10 12-13-02, 08:40 PM

So is my P model. Whenever I fly into rain it starts leaking on my foot! And on the avionics stack. Really messes things up. So the number one item on the list for the annual next month is to find that darn leak!! Number 2 item is replacing BOTH engines. I should be in good shape by the time we get to Nashville. Broke, but in good shape.

Guy Paris · #11 12-14-02, 02:24 PM

I would have thought that a positive pressure would keep anything from entering the pressurized cabin!!! My normal G has not leaked yet. What we do any time the two hatches are opened is put DC 4 on the rubber gasket and in the screw holes. Hope I haven't jinksed it!! She is in annual now and things are going ok. Going to change the 92 SB. hoses with CESSNA (ouch) hoses.... The front engine compressions, 1500+ hours TT, were a bit higher than the rear... Guy, old72driver....

Don Hickman · #12 12-15-02, 01:51 PM

I would have thought so, too. But that's not how it is. And we've put lots of sealant goop on those access panels and everywhere else but to no avail. Bob Cook has suggested using a leaf blower for pressure testing and that's what we're going to do during the annual next month. Hope we find the leak.

Bob Cook · #13 12-15-02, 02:38 PM

Don

The water pressure on the hull needs to be greater than 3.4 lbs per sq inch before it will leaks. I can only assume that it might be around the windows where there is a reasonable pressure exerted and it is coming in around the window seal. Kevin mentioning the replacement of the windows due to etched plexiglass might be the culpret. It might be worthwhile condsidering sealant but the leaf blow trick would certainly show it up. I am guessing along the top of the window. If you find water in the AC after a big rain then i might suspect the hatch covers. I don't think it is coming from inside firewall.

Sure is a mystery that only pressurization testing will solve. BTW check all the rivets along where the instrument panel attaches. They seem to losen up and cause leaks.

let us know the results. Are you heading to mx for Xmas ?

Bob

Don Hickman · #14 12-15-02, 02:56 PM

Thanks, Bob. I've been passing your advice along to my mechanic and we're going to find that leak next month!

We're heading out to Mexico on the 26th. Back on the 10th. Plane goes in for annual as soon as we get back and for 2 new engines also. I'm tired of constantly trying to fix stuff so I'm going to replace it. Should have just bitten the bullet and put new engines in it when I got it. The 220 hours I've put on it in the last 12 months have been costly!

Oh, and the pressure doesn't have to be more than 3.4 in order for the plane to leak. I've not ever been able to get more than a 2 pound differential. So I'm assuming I've got a pretty good air leak somewhere.