I Want to Buy a Mooney Ovation

What Should I Do?


By Joe Frisolone
East Coast Aviation

{Originally printed in the August/September 1999 Issue of the MAPA LOG, Mooney Aircraft Pilots Association's monthly magazine.}

The Mooney Ovation model M20R first took flight in 1994. From the beginning this phenomenal aircraft has been the leading model sold by the highly skilled craftsman of Mooney Aircraft Corporation. By the time you read this article Mooney will have manufactured and delivered serial number 191, proudly sold by East Coast Aviation. Sorry, had to get that in!

If you are not familiar with the Ovation then you may be wondering why this speed demon has even surpassed the venerable Mooney MSE in units manufactured since it was first introduced. Well, it is simple, really. The Mooney Ovation is the fastest single engine normally aspirated aircraft ever produced. Take that Beech Bonanza, had to get that in too! Anyway, once again the superior engineers at Mooney Aircraft Corporation came up with the optimal combination of airframe and powerplant to deliver an incredible combination of efficiency and speeeeeed.
T he Mooney Ovation combines the "long body" fuselage first introduced with the Mooney Porsche and then perfected with the Mooney TLS/Bravo with the Teledyne Continental Motors 10550G engine. The engine horsepower is derated to 280 turning at 2500 RPM. While the TLS/Bravo is the fastest Mooney built thus far, this distinction is based on high altitude flying. In fact, the Ovation is a tad faster than the TLS/Bravo at or below 8000 ft MSL.

So, you want to purchase a used Ovation and want to know what you should took for. Well, I will get to that, but first the disclaimers. In my first article regarding pre-purchase inspections which debuted in the June issue of the MAPA Log I told you that I intended to run a series of three articles regarding pre-purchase inspections of all the different models of Mooney Aircraft. When I sat down to write article #2, I realized that I could fill the space allotted in the MAPA Log just on the TLS/Bravo alone. So I decided to concentrate' on individual models as well as grouping certain models as I go. My goal and intentions are to provide you with the "inside" information you need to achieve your goal of purchasing a good safe used Mooney aircraft. Now, having said that; disclaimer #2: There are several redundancies from one model to another, especially between the Ovation and the TLS/Bravo. Therefore, you will notice some of the same things stated in this article as the previous article I wrote regarding pre-purchase inspections of the TLS/Bravo. Simply put, both aircraft have basically the same airframe with different engines. And, rather than have you refer to a previous article for a specific point, I believe it will be more beneficial for the reader if I include pertinent information even if it is redundant to a previous article.

Let's get started. After the flight test, we need to perform the differential compression test. For those of you converting from Lycoming powered Mooneys to a Continental powered Mooney, this may be the biggest adjustment you will make. The acceptable compression readings of a Continental engine will typically be much lower than those of Lycoming engines. Teledyne Continental has printed Service Bulletin M84-15 which dictates the approved procedure and acceptable compression readings for their engines.

In this Service Bulletin they discuss the difference between "static leakage" and "dynamic leakage." Static leakage is air leakage past the valves and dynamic leakage is air leakage past the compression rings. In Service Bulletin M84-15, Continental states that zero static air leakage is acceptable. However, dynamic air leakage is another story. Teledyne Continental will allow incredibly low differential compression readings if the low reading is due to a dynamic air leakage How low is acceptable? Well that varies depending on the tester you are using. Let me try to explain this to you. In the afore-mentioned Service Bulletin, Continental specifies a special tool (p/n646953) that must be used to calibrate the differential compression tester the Technician uses to perform the differential compression tests. Upon application of the special tool with the differential compression testor, a technician will then know the lowest acceptable value for differential compression tests performed on Continental engines. For example, at East Coast Aviation both of our calibrated differential compression testers are at or about 48/80 P.S.I. Thus, according to Teledyne Continental Motors, differential compression readings as low as 48/80 PS.I. are acceptable so long as the air leakage is past the compression rings and not the valves.

Now, after that long winded explanation on what Continental considers acceptable, let me explain what our standards are at East Coast Aviation. First of all, if performing an Annual Inspection we wouldn't return to service any engine that had a cylinder or cylinders with differential compression reading of 48/80 PS.I. How low is too low depends on several factors. The total time of the cylinders. The relationship of all cylinder compression readings compared to each other and what the compression readings were the last time a differential compression check was performed. Also, when comparing the differential compression readings subsequent to the current readings, the amount of flight time that has elapsed has relevance.

Another indication of the health of a cylinder is what the firing end of the spark plugs look like. It's an old cliche but spark plugs do tell a story. For example, if they are damp with oil you can assume that cylinder they came out of has worn oil control rings. Also, if your maintenance facility owns a borescope, the cylinders can be examined for rust or pitting as well as excessive carbon build-up. In the end, experienced maintenance personnel should know how to interpolate the differential compression readings and examine the spark plugs and cylinders to determine the health of the cylinders. If the technicians you choose to perform the pre-purchase inspection are not familiar with Teledyne Continental Motors Service Bulletin M84-15 and have not calibrated their differential compression tester, choose another shop.

OK, enough already about differential compression tests. What else should we pay attention to inside the cowlings. In case you haven't noticed, I like to use bullet points on a regular basis, so here we go:

What should you took for on the airframe? If the aircraft is equipped with a TKS system, ensure all airframe and windshield pumps are in good working order. We have experienced pump failuresw in the field. We believe the primary reason for failure is the lack of usage by the owner/operator! Also, because fluid comes out doesn't necessarily mean the pumps are operating properly, the operating pressure is critical. If an owner/operator is a heavy TKS user, inspect the bellcrank needle bearings in the empennage for rust. The TKS fluid seems to displace the lubricant applied to these components during service, allowing rust to occur. Carefully inspect the fuel tank area for leakage.

Inspect the tall for excess play at the tail trim link mechanism. Also, check for excess play at the two hinge bolts. The two elevators and rudder utilize several rivets called, "Cherry Max" rivets. Inspect these rivets for signs of loosening. Occasionally, we have seen these rivets start to loosen or "work" as technicians call it in the field. You can identify this by a trail of black soot aft of the rivets. Technicians in the field call this, "smoking rivets".

Check the top sides of the wing flaps for excess chaffing. All Mooney wing flaps will chafe to a certain degree. However, if the flap attaching and actuating hardware is not maintained to near new tolerances, excess wing flap chaffing will occur.

Check the landing gear shock discs for excess compression. The maximum allowable compression is 5/8". Also, if you jack the aircraft and can rotate the shock disc's one half hour later, the shock discs require replacement.

Check the landing gear rigging and play amongst all of the actuating rod ends. If the aircraft was maintained by well meaning technicians that are not very familiar with the Ovation landing gear system, there may be problems. Pay particular attention to the roll pins that are used to secure each rod end to its respective push pull tube. We note play in this area from time to time. A nuisance, however a common problem, the arm rest attached to the pilot's seat is commonly broken.

Check the electric fuel pump low output regulator for proper operation. We have seen many instances where this function was inoperative or not properly adjusted in the field.

As mentioned previously, there are many similarities between the TLS/Bravo airframe and the Ovation airframe. Also, keep in mind I have not mentioned airworthiness directives or manufacturers service bulletins. I believe that AD's & SBs are routine easy items to research and verify, therefore assume that any competent maintenance facility you contract with will utilize current data to verify compliance. If you focus on the items I have mentioned, you will employ years of experience encompassing several Annual and pre-purchase inspections of Mooney Ovation's. This information coupled with diligent maintenance personnel will provide you with one of the greatest aircraft ever built... The Mooney Ovation!