Cessna O-2A 67-21424
Cessna O-2A67-21424

Owning and maintaining any airplane is tough. It is more challenging when that airplane is a warbird, with specialized maintenance and parts challenges. The O-2 has definite advantages over some other Warbirds, like a P-51 or a B-17, but challenges exist.

2 August 2023


Yet ANOTHER year since my last post! Well, the last one was posted after I came back from AirVenture 2022. I mentioned how the HSI went bad in IMC. The O-2 does not have a vacuum system, everything is electric. Tht means is fails less often, but when it does fail, it is more expensive. In this case, my local avionics sgop happened to have an eact same model refurbished HSI on the shelf, from someone who upgraded to a full digital system. So, all in all, it was much less expesive and much faster than it might have been.


I then has a series of landing gear difficulties, beginning with a microswitch failing, so the airplane didn't know that the landing gear were down and locked. Then there was a small leak in the hydralic system which was just enough to let air into the system. Hydraulic systems don't work well on air. When that got fixed, I put it in for annual on May 16, with the only major fix being to change a tire and send my engine monitor out for some deferred warranty work. It is still not flying. So, no OSH this year. The series of unfortunate events began with no indicated manifold pressure on either the monitor or the analog instrument. After lots of troubleshooting, we determined that it was a problem in the engine monitor. It was, and so back to the manufacturer for repair. Then, on ts post maitenance test flight, the monitor indicated that there was a problem with the front engine, possibly the magneto. Since the shop had just calibrated the timing, they didn't think that was likely. It was, and in the next attempt to fly, the magneto failed completely. What should have been a week to ten day overhaul and reinstallation has not been more than a month. I will post again when I it once again slips the surly bounds of earth.


7 August 2022


 I can't believe that is has almost been a year since I last posted. First, I think that a picture of the prop damage from last year is appropriate: 



It took about a month to get the prop back and installed. That was in October. I was then able to fly the airplane back to Manassas to have the engine removed and shipped out for inspection. The good news was no damage to the internal vcompanents of the engine (as expected.) The bad news was there were issues discovered that had to be addressed. These include:

-Crankshaft had to be replaced due to pitting. 
-Crankcase was overhauled, due to significant fretting damage. 
-Camshaft had to be replaced, also due to pitting. 
-Lifters  replaced (goes with the camshaft). 
-Ignition harness was replaced (old. would have been replaced at next annual, anyway.)
-Oil cooler was replaced. (When it was removed, there was significant damage observed on the under-side)
-Cylinders needed repair/rehoning. 
-The starter adapter required an overhaul.


Before I approved any work, I got a second opinion by Savvy Maintenance, and the experts there confirmed that the work needed to be done. The really expensice stuff most likely existed before I bought he airplane, due to its prior life on the Atlantic coast in FL, doing Whale population surveys.
In the end, I got the equivalent of a field overhaul at about than half of the out of my own pocket expense of what would normally be. The plane wasn't put back together until the first week in JULY! (Supply chain problems affecting all aircraft repair, and especially engine teardowns.) But it was just in tie to go to Oshkosh!


Then...the audio panel went bad. OUTSTANDING advice and suport from PS engineering and Aircraft Spruce. I installed a new PS 7000 MBT while I was in Oshkosh. Then, on the way back, my HSI broke. In instrument conditions, of course. This meant navigation using the magnetic compass, GPS direction, and hand flying the airplane for about an hour and a half. Fun. 
Other than that, the airplane is fine.




31 August 2021: 

It was the best of times and the worst of times. Best of times: I finally got the fuel system re-calibrated, the engine monitor properly set up and calibrated. Not complaining, but all of this was not inexpensive. In any case, everything was A-OK for the trip back to EAA AirVenture at OSH. Great flying there and flying in the airshow on Wednesday. The monitor really helps to maintain confidence that everything is fine. Oh, about the cylinder running "hot." I had a long chat with Continental and two different tech reps said that there was nothing wrong and the cylinder tempeatures are well within the normal range.


Worst of times (but could have been worse yet.) As a reminder, I got new props less than two years ago and, at the same time, got the fuel injection system overhauled, the rear magnetos overhauled, a new alternator for the rear engine, and, as I said above, the fuel system recalibrated. 36 hours flight time since all of that, including to and from Oshkosh. THEN, on August 21st, I flew from Manassas to Dulles International Airport to for participate in a static display at the Udvar-Hazy annex to the National Air and Space Museum. As we were moving the airplane by hand into its parking spot, one of the helpers said I needed to look at my rear prop. The best way to describe it is that it looks like it hit a chain link fence! I have NO IDEA what it hit, or even at what phase of flight the impact occurred. The engine monitor data shows NO RPM variation, no spike in MP, oil pressure, or voltage. I have had various opinions on what it might have been by three different A&Ps and a NASA engineer. The most likely seems to be picking up a piece of angle iron while taxiing at Dulles. But there are disturbingly good arguments that it was a BULLET!


Anyway, now I need new prop blades, prop hub and governor overhauled, and the engine needs to be completely torn down (complete disassembly) inspection, repair, certain mandatory new parts, overhauled magnetos, then reassembled. Oh, and the airplane is at IAD. Insurer says they will pay for everything, which is great, but I am still looking at 4 months down-time. But when it is done, I will – or should – have a GREAT rear engine and associated systems.


15 May 2021: Well it actually took until the 2d week of March to get 424 into annual inspection, and I was only able to start it then because a new maintenance shop had just opened up on the airport. Great people, pretty young, all military trained airplane mechanics. As a result, they really enjoyed working on the plane, and I enjoyed working with the. The plane was in and out in ONE WEEK! However, it then too some time after that to fix little bugs an annoyances, mostly associated with the new engine monitor. We had to track down apparrent leaks in the induction system. Yes, there were minor leaks we found and fixed, but we really didn't solve the issue until we determined that the line leading from the manifold pressure line to the new engine monitor had never had the rubber hose fitting clamped, so it was sucking air into the system there. Then, the monitor showed little problems that I had been blissfully unaware of up until then -- like the #1 cyliner on the rear engine was running very hot. So we shored up some more induction leaks and moved a large "SCAT" hose that was blocking airflow to that cylinder. The only thing left is some minor adjustment to the idle setting and it will be ready for the summer flying season.


Oh, the reason why the prop spun when the master was turn on. The starter contactor (solenoid) got stuck. Cheap fix as far as aiplane parts go.


30 January 2021

Well, it is really emabarrasing that I have not updated this website in, I gues six years. I still get iquiries from time to time, so people are looking at it. In any case, the joys of warbird ownership continue. Since the last posting, I have had to install two new props, overhauled the front and rear fuel systems, new fuel hoses on the front (the back needs to be taken care of this year), new alternator and coupling on the back, overhauled the back magneto, along with various odds and ends, like a new Hobbs meter. Right now, it is awaiting installation of a font engine starter contactor. Something that REALLY gets your attention is when turning on the battery causes the prop to spin!  You know, all pilots are taught to shout clear before turning the master switch on. Now I know why! Curously, the maintenance manual for the O-2 actually has a warnining about that. That warning, however, is missiding from the operator's manual (Dash 1 in USAF speak.)


Most exciting is that I have installed an Insight G4T engine monitor! This gives me more information about my engines than I ever thought about asking. As the engines age and the engine gauges get ever older, I began to doubt their accuracy. The new monitor will give me precise information about things like true RPM, manifold pressure, exhaust gas temperature and cylinder head temp for each engine, equivalent horsepower produced by each engine, both as a percent and total horsepower, and even engine vibration. I hope that it will geve me some peace of mid and confidence when making the long trip to Oshkosh and other locations, especially IFR. It will help plane maintenance ahaead of undesirable events, too. The set up is not quite complete, but the starter contactor issue has delayed things. Getting a new cntactor was easy. Waiting on the maintenance shop was something else. All shops in the area have a long waiting list, if they will see you at all. (Sort of like trying to buy ammunition.)


And now it is time for the annual inspection...

January 2015

More joys in antique Warbird ownership.

At the end of November, I took advantage of some really nice weather and went out to a nearby, nice, but relatively quiet airfield to practice overhead approaches. The fuel is also significantly cheaper there than at my home airport. Everything fine until leaving the pattern, when the landing gear became an issue.

As a side comment, I do not put the landing gear away until the airplane is 500’ AGL. Acceleration altitude: 500’ AGL; confirm airspeed (not too slow not too fast); ops normal; and then the gear come up; flaps come up and climb power set. It is NOT a good idea to put the Skypig’s gear up at two indications of PRC. The gear retraction introduces so much drag that there are estimates of 250 fpm DESCENT doing that with an engine out. Don’t touch nothin’ until 500’AGL.

Anyway, turning crosswind, I put the gear handle up. Everything seemed normal, gear were moving and there was the familiar “clunk” of the gear locking up. BUT…the handle did not pop into up neutral and the amber light did not come on. (Note: This is one of those civilian conversion issues. In the USAF O-2A, the amber light is on in transit and goes out when the gear are locked up. When registering it for normal category it has to match the O-2B/C-337 process of not turning on until the gear are locked up.) I tapped the handle. The book says that sometimes it sticks up and a tap will set it. (although the amber light should already be lit.) Didn’t move. Then I notice that my airspeed is way low for the power setting. I do the logical thing to do ONCE. Reset the landing gear. Everything seems normal, gear come down, comfortable thump, green light on. So we go up again. No light, handle does not pop to up neutral. It is now about sunset and I can’t see much from the wing mounted mirror, although it looks like the gear are up but the front doors are open. I proceed home and have a wonderfully normal landing.

Later, I open and close the doors using the hand pumps. Everything seems fine. No visible obstruction. A week later, next good flying weather, I do the logical thing. I take it around the pattern. This time I have my 12 year old son with my oh so precious former East German Zeiss binocular watching me. Being somewhat more worried about the binocular than the landing gear I head skyward. Same thing. It is now daylight and when I look in the mirror it looks like all landing gear doors are open. Now I have fun. I tell the tower I may have a landing gear problem. They confirm gear up, doors open. (My son provided a somewhat more detailed but consistent description later.) Every other airplane in or approaching the pattern starts radio chatter expecting the field to be closed for an emergency. There was none, happily.

Anyway, after consultation with my mechanic and some extensive troubleshooting, we discover that the bolt and roller bearing that comes into contact with the up-lock switch are missing! Gone. Worse than gone. The bolt broke off about 1/16” below the collar of the nose gear trunion. Guess what that meant?

a) We were going to have a wonderful time finding an obscure part for a 47 year old airplane that has been out of service and out of production for 35 years

b) That we had to remove the nose gear assembly to get the old bolt out; or

c) Both

Fortunately, the answer was not (c) but (b) was bad enough. The good news was that when we got the gear out we found the broken bolt and roller bearing in the wheel well (you don’t have to be good if you are lucky.) Further, the bolt was a standard AN bolt! The bad news is that even with contributing my active labor and time off of work, it was 13 hours of shop time to take the nose gear out, rout the remnants old bolt out and reinstall everything.

But the story is not over! When we contacted Don Nieser of Commodore Aerospace, he checked the O-2s he has for rebuild. He found one up-lock roller broken and three bent! Every time the gear retracts, the roller hits the up-lock. After 8,000 hours and 47 years of strikes, the bolt weakens.

I would say that it is an easy enough repair to make if you don’t wait until it breaks. The bolt can be reached with the landing gear down and locked. The bolt itself is a standard AN bolt that costs about 75 cents. The catch is that, at least for mine, it was in so tight that it could not be removed with an easy out. My mechanic broke 3 bits trying that. He finally had to carefully drill it completely out and then pick out the threats (hence part of the 13 hours shop time.)

If you can get a good grip on it and work it out without removing the landing gear, replacing the bolt before it breaks might be worth a thought.

And with regard to the November 10 post. It only seems to drip fuel in my hangar. Over a week in the maintenance shop, on jacks, fuel selectors on and not so much as a drop of fuel leaked. Gremlins.

10 Nov 14

Nothing significant to report, which is almost a miracle. Airplanes do not like to sit, and for various reasons, 424 sat for over a month during the fall temperature changes. I went out to the plane to fly some Young Eagles for the EAA on Saturday and found the right brake pedal went all the way to the ground and some leaking from one of the fuel drain lines of the rear engine. Put 5606H in the affected cylinder, pumped it all through the lines and everything seems fine. No obvious leaks. Looking again today with the sun shining into the hangar, I can see a couple of spot where something may have dripped through the line and out the relief valve. I will probably spend some time with it tomorrow. The fuel drain line leak has happened before. Some drips between Saturday and today (Monday) by no observable fuel loss from the calibrated fuel dip stick. So, of the time being, I make sure the fuel selector valves are set to OFF and will dive back into the maintenance manual before talking to Geoff (my mechanic).

4 July

Annual inspection was completed a couple of weeks ago. Major events included new tires (there is an age limit as well as a wear limit) and repair to a fuel tank. I had been suspicious that one fuel tank was losing fuel somehow. It turned out that a patch had been improperly sealed by the previous owner and the sealant deteriorated because of contact with (wait for it…) AVGAS. The rest of the story…When the O-2As are registered as civilian aircraft, certain things have to be done to "de-militarize" them. One of these is removing the foam from the fuel tank which makes it fire retardant. Not a major concern since no one SHOULD be shooting at us. A hole has to be cut into the top of the tank, the foam removed, and then the tank patched. The hole is at the very top of the outboard main fuel tank. This means that fuel only came into contact with the (bad) sealant when the tank was full. Therefore it took about 10 years to turn the sealant into goo. All fixed now. (The bank account will take time to recover.) I also had the prop tips painted a proper yellow and swapped out the A-37 gunsight that came with the airplane for a proper O-2A gunsight (and then get it working). Related to that is another little thing. Someone from the local FAA office made an issue with my mechanic about the weapons pylons on the plane. He said that I could not fly the airplane with them on the wings unless I re-registered the airplane as experimental. Don Nieser at Commodore Areospace was able to provide the letter from FAA aircraft certification branch that confirmed that the airplane was originally certified with the pylons (and military seat belts, military specific engine gauges, jettisonable door, etc.) and did NOT need special permission to fly with that equipment installed. The focus now are those little post-maintenance things that always seem to pop-up (like the front EGT gauge which I just replaced last year). The major effort is cosmetic work to get the airplane ready to go to EAA AirVenture in a few weeks.

25 May 2014

OK, since the last entry, the brake problem was resolved. Thanks again to Don Neiser of Commodore Aerospace. Everything was fixed before the Manassas Airshow and I was able to make a few pre-show passes with the mock-up weapons installed on the hard points. Right now it is in for annual inspection. I want to spend resources on continuing to improve the appearance, but those resources keep getting diverted towards fixing the things that just need to be replaced in a 46 year old airplane. These events include: Replace wing strut fairings (one separated rather dramatically in flight enroute to OSH last year.) New tires (airplane tires both wear out and age out. This was age-deterioration.) Prop repainted (finally getting the yellow tips it was supposed to have had.) Swapped out the A-37 gunsight which the previous owner had installed for the correct O-2A gunsight. (Thanks again to Don Neiser.) Fixed the copilot seat (worth a post all by itself.) The most interesting piece has been repair of one of the main fuel tanks. My A&P noted Avgas leaking everywhere. NOT a good thing. He had to remove the tank. (It is only money.) He found that, in removing the foam from the tank (the stuff that made it self-sealing), the previous owner had not sealed the tank properly. Either it was the wrong sealer or it was mixed improperly. The end result was that AVGAS was eating through the sealant. Because the patch was on the top of the tank, AVGAS could not really get to it (or the tank leak) unless the main tank was full. Hence it took a long time for the sealant to finally turn into goo. The nice thing is that I will have it done in time for some serious work on fairings, plastic trip repair, and touch-up paint before the next two events: National Air and Space Museum on 14 June and then Oshkosh in July.

9 March 2014

Building on the my comment below that there is nothing cheap about owning a Warbird. Let me add, "or easy" to that. Of course, the brake problem could not have been anything as simple as a bleed valve. It was the brake housing itself that cracked (47 years old. Lots of hard use before and after sitting in the Arizona sun for 15 years without maintenance.) On the O-2A page of this website, I listed "Heavy Duty Brakes" as being one of the USAF changes. Yep. Than included the housing. Normal Cessna part numbers for Cessna C337B thru D right brake housing is C163030-0404 or 0406. For the O-2 (Cessna M337B) it is -0408. Winter seems to be finally over, but the sky pig is grounded looking for a part that has probably been out of production since 1978 or earlier.

21 Feb 2014

On the EAA Warbirds forum, there is a thread going responding to someone who is looking for an inexpensive warbird. The general consensus in response to him is that there is no such thing. 424 is a case in point. I have a world of respect for the guys who can devote the time and effort to keep up a Mustang or a Texan. Most of these people have figured out corporate support, partnerships, and other means to feed their plane and passion. Many others are doing it as their own passion, with the patience and support of their family. Even though the O-2 is nowhere near the same level as those North American airplanes, it definitely shares some of the warbird upkeep.

First thing to keep in mind is that all of these warbirds are old. The Vietnam era planes are the youngest, at 40+ years. Now, that is still younger than most or all of the B-52 and C-130 airframes in the USAF. On the other hand, I (and other warbird owners) do not have the resources of the United States Air Force to throw at it to keep it repaired and flying. For one thing, that means that spare parts, which are always expensive for any airplane, become even more rare and more expensive for airplanes no longer in production or part of the DoD supply chain. Parts wear out. O-rings get hard. Plexiglass crazes. And then there is corrosion. Owners of antique cars have similar problems, and I respect what they do, too.

A 45 year old civilian C-337 would also be a challenge to keep up for these same reasons. As I pointed out on the "Plane" page, the O-2A (Cessna designation M337B) is NOT exactly a civilian Skymaster. All of the differences listed on that page are associated with different parts. Since the USAF only bought 501 of these to begin with, that adds to the problem. Some of these parts were and are common to other military equipment. Some are unique to the O-2, and within that, the O-2A, and within that, the difference between early and late model O-2As.

I am not complaining, just explaining. I have no desire to swap 424 for a civilian Skymaster or a newer airplane (although a C-206 seems nice from time to time.)

Thankfully, there are some people who are dedicated to keeping the 50 or so O-2As that remain flying doing just that. Commodore Aerospace, headed up by Don Nieser deserves special mention -- and deserves a visit to his website. Not only is he a great source for parts and advice, he also restores airplanes and gets them out and flying again. Thankfully, too, BECAUSE of its former history, I don't need to worry so much about corrosion; the entire airframe having been thoroughly covered in zinc chromate.

Parts aside, I feel a responsibility to keep the airplane up properly, that is, as a living heritage of our nation's military history and to the men who fought for our country. That means that I am somewhat constrained by what I can and can't do with the plane. I have to keep it looking right on the outside. Inside I have to make trade-offs as it has the dual purpose of being a family plane AND it has to fly in the modern airspace system. I have seen some O-2As which are just about as original on the inside as they can be. I am glad that those pilots are out there. Me, I make compromises. I have a newer attitude indicator, a Garmin 530W with GTX 330 (I can't use the IFF transponder…I think) and an STEC 50 autopilot. I also have a Shadin fuel flow gauge with Gamijectors. If the airplanes were still in service, I reason, they would have been upgraded even more than that.

Anyway, I am NOT complaining. It is, however, a significantly greater challenge than owning other airplanes. On the plus side, it is easier to justify paying hangar rent.

All of the above is because I went out to fly today…the first time in a month because polar freeze we have all been enjoying. Plane started right up (I have a sum heater and trickle charger) only to find no pressure for the right brake. The 45 year old right brake bleed line did't survive the freeze.

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© 2022, Christopher T. Mayer.