Covington Aircraft - Quality Service

Your aircraft will always be in our possession in one of our climate controlled hangars. Only qualified personnel will move the aircraft and only if absolutely necessary, for maintenance purposes, will we enter the aircraft itself.

Below is a map of Okmulgee that will give you driving directions, but if you’re flying in we are identified as KOKM. Customers also frequently fly into Tulsa, OK and drive 35 miles south to our location. If you need a ride from Tulsa International give us a call.


Give us a call anyway! Not every engine issue demands a complete overhaul. We do maintenance level work on ALL PT6A engines and most of the time we can still take care of any issue you have. As stated on some of the other FAQ's, if we can't help you we will point you to someone who can! We're not in the business to say, "sorry, we can't help you!"

The list is short and we've kept it that way for a reason. You shouldn't wonder if "your guy" at Covington is still around or how many times you will be transferred before you get a warm body. The people you will be talking to, combined, have over 100 years of experience. Yes, your Covington guy is here.

Parts: Robert Ramirez or Ted Neal
Customer Technical Support: Ron Hollis
General Questions and Quotes: David Hamilton
AOG: 1-800-324-8320
Account Receivables and Payables: Annette Stewart

It's our intention to treat you like you're our only customer! We have grown our business one aircraft, one customer at a time and we are not just after the quick sale. We're after your patronage and a relationship that addresses more than just an engine at the end of the day. Looking out for our customer's best interests doesn't mean we want to sell you something. We intend to make you feel appreciated.

Yes we do. We do annuals, 100 hours and most service related work on any airframe. We have experienced, FLIGHT SAFETY trained personnel ready to take care of your needs. If your work scope is beyond our capabilities, we will recommend someone who can help you, or assist us, in making sure your expectations are met.

Yes we can! We prefer to do it at our new, 47,000 square foot hangar facility in Okmulgee but we will come to your location if you prefer. 

Covington takes care of their customers! We haven’t been growing for the last 38 years because we skirt around problems. Rest assured our goal is to support you in your time of need. There are two potential warranty directions: The first is Covington Warranty, basically if you had work done through us we are the folks to make sure it exceeds your expectations. Secondly is Pratt & Whitney Canada Warranty. As a Distributor and Designated Overhaul Facility for Pratt & Whitney we are authorized to make decisions that will get warranty on your side where it was intended to be when you bought the engine. We deal with Pratt warranty on a regular basis; let us get the right people in your corner as soon as you have an issue.

Give us a call and lets talk. Lets find out where you and your engine are, and where you want to be. Call or email David Hamilton our VP of the Turbine facility and he will get the ball rolling.

We're so glad you asked! We would like to do that for you. We are fortunate to have many customers that operate medium to larger fleets. We frequently help them track engine information and conditions, and with that information, build a "plan of attack" that both parties feel will keep the engine and aircraft where it needs to be maintenance wise with as little disruption to your flight schedule as possible. Let's see what we can do for you. Besides, it's a free service to our customers. Remember, you're not alone; Covington will be with you every step of the way.

Tell us what you want. FAST turn times can be accomplished by exchanging parts but may not always be the best choice for every customer. If you have a low time core you're placing yourself at a disadvantage to exchange parts just to save 10 or 15 days. The average turn time is 45 days. Let us know what you need and we will tell you if we can meet your requirements.

Every engine is different. Several factors determine the final estimate to overhaul your engine. How old is it? What service bulletin levels are already incorporated in the engine? How many hours are on it? How many cycles are remaining and how has it been maintained? All these answers play a part in determining your final estimate. We have "generic" quotes that can give you the average price if you let us know your engine model, but the best way to get an accurate quote is to provide us with the details listed above and then we can produce a custom budgetary estimate to overhaul your engine.


The 100 hour / Annual Inspection

This is the second topic in the series about the 100 hour / annual
inspection. This series focuses on maintenance performed during an
effective 100 hr. inspection on R1340 and R985 engines:

1. Oil Change with filter/screen & sump checks.
2. Valve adjustment - Positive or compression.
3. Ignition timing check - Spark plug servicing.
4. Compression check - differential.
5. Air filter and carb - heat system check.
6. Fuel System Screens.
7. Cylinder Head Checks.

Valve adjustments provide you with an excellent opportunity to
check the hottest side of your engine for unusual wear.

General Info on Valve Adjustment:

The most potential for required adjustment of the valves usually
occurs at the first 100 hr. valve check. Always question; Why when
more than 1 turn on an adjusting screw (either way) is required to
obtain a good clearance. Problems such as bent/broken pushrod,
recessed valve seats, stretched valve stems, worn or failing rocker
bearings are often first detected during a valve adjustment!

R-1340 Exhaust pushrods are roughly 1/8 inch shorter than the intake
pushrods. R-985 exhaust and intake pushrods are the same part
number and can be interchanged. The manual recommends marking
the tips Ex for exhaust and In for intake, a practice that has been
dropped over time. However, those markings still provide some
excitement when a novice finds pushrod tips marked intake in an
exhaust location.

It s important to know whether your R-1340 engine is equipped with
steel exhaust pushrods (unusual!) or aluminum. Engines with steel
exhaust pushrods require adjustment utilizing the positive method. R-
985 engines do not have a steel exhaust pushrod option. We currently
install aluminum pushrods in our overhauled 1340s.

Be Patient! Remember that valve adjustment on an R-1340 or R-985
engine is not an exact science and a feel for the process will develop
with practice. I prefer the Compression method of adjustment to the
"positive" method. If you set them one way and double-checked it the
other, you would be hard pressed to find any differences in the final

The Compression Method of valve adjustment on the R-1340 engines
is described in the Pratt & Whitney PN: 123440 Overhaul Manual as:
Valve Clearance Adjustment (Optional Method). It reads as follows:

The valve clearances are adjusted in a sequence which conforms to the firing
order of the cylinders: 1,3,5,7,9,2,4,6,8.

Back off all the valve clearance adjusting screws until at least six threads are
visible above the rocker. Turn the crankshaft in the normal direction of rotation
until No. 1 piston is at T.D.C. (top dead center) of the compression stroke. Insert a
0.010 inch leaf of the clearance gage between the valve adjusting screw and valve
stems on No. 1 cylinder, and tighten the adjusting screw until 0.010 inch clearance is
obtained. Tighten the valve adjusting screw locknut to a torque of 300 to 350 pound-inches.

After the valves in No. 1 cylinder have been adjusted, rotate the crankshaft
until No. 3 piston is at T.D.C. of the compression stroke. Adjust the valves in the
same manner as described for No. 1 cylinder.

Adjust the clearances of the valves in the remaining cylinder(s), always
turning the piston to exact T.D.C. before making the adjustment.

After the valves in all nine cylinders have been adjusted, rotate the
crankshaft two complete revolutions and recheck the clearances. Reset any valve
clearance found below 0.010 inch. Do not disturb a greater clearance unless it is in
excess of 0.025 inch.

I normally set each valve at .010" clearance (slight drag on .010")
then check for at least .010 and no more than .017 (book says .025").
Each valve should be checked at least 4 times, as the cam has 4 sets
of lobes. Valve Adjuster lock nuts should be torqued 300 to 350 in/lbs.

I find that it s generally achievable to establish clearances between
.010 inch and 0.017 inch. Don t be upset if you have one or two that
are slightly looser than that when finished. If you are installing a
replacement cylinder and don t have time to adjust all the valves, the
valves on the replacement cylinder should be adjusted slightly loose
using 0.015 inch as minimum clearance. Full engine valve adjustment
should be done as soon as is practical following a cylinder
replacement. Slightly loose is better than slightly tight!

The engine Maintenance Manual valve adjusting instructions are
posted on the web-site for your review! Call us for tips on making this
involved maintenance less painful!

Fly Safe!
Ron Hollis

The 100 hour / Annual Inspection

It's annual inspection season again. I guess it's like death and taxes...sure to come around. Lots of folks have asked "what should I have done to my engine during the annual?" The engine maintenance manual, part number 118611 contains the Periodic Inspection Tables listing the Requirements for the A (50 hr), B (100 hour inspection), C (200 hour) and D (Midway to Overhaul) inspections on R1340 and R985 engines. Of the requirements listed I'd like to offer some recommendations on seven of the heavyweights .

1. Oil Change with filter/screen & sump checks.
2. Valve adjustment - Positive or compression.
3. Ignition timing check - Spark plug servicing.
4. Compression check - differential.
5. Air filter and carb - heat system check.
6. Fuel System Screens.
7. Cylinder Head Checks.

Since this is a bit lengthy let s focus on one topic per article:

Oil changes: The periodic table indicates the time between oil changes should be determined by the type, and condition, of engine operation. As a general rule we recommend they be done on 25-50 hr. intervals, or at 90 day intervals. If you only fly 25-30 hours a year, a once a year oil change wouldn't be frequent enough. You may cause engine damage due to acids and moisture accumulation in the oil. It is absolutely essential to drain both oil sump plugs and check the engine filter or screen at every oil change. If you have a spin-on or sock type filter, it should be cut open and checked for metal contamination.

It s interesting that the engine's oil "screen" is a pressure side screen filtering the oil after it passes through the pressure pump but before it flows throughout the engine. The after-market filters are all scavenge oil filters. They filter the scavenge oil just before it flows into the cooler. This is good because it helps keep contamination out of the oil cooler and oil tank keeping the entire oil system cleaner. However, because it is an outlet-oil filter, it will effectively mask the engine oil screen. The engine oil screen is the historic location to check for metal contamination. If you don t cut the spin-on filter open and inspect the element you could well miss discovering metal shavings being generated by some form of distress in the engine!

The Scavenge oil system has a "finger screen" in the sump that prevents solid material from being pulled into the scavenge pump impeller gears. The screen is located inside the sump and can be accessed by loosening the attach bolts on the lower end of the larger of the two metal scavenge tubes attached to the sump (R-1340) or the Large 1 ¼ in hex plug on the rear of the sump mid-way up from the bottom(R-985). This screen is designed to prevent large pieces of metal from being sucked into the oil pump, resulting in pump and pump drive failure. The periodic inspection tables calls for removal and cleaning of this screen at 50 and 100 hours. It is fortunate that the sides of the 1340 engine screen can be viewed through the rear oil sump drain plug using a strong light (and after the oil stops dripping!).

The oil sump is located between cylinders number 5 and 6 and is equipped with two oil drain plugs. The front drain plug on the R-1340 accesses the rocker-box scavenge oil sump while the rear drain plug accesses the engine main case scavenge oil sump. The front drain plug of the R-985 accesses the engine main case scavenge oil sump while the rear drain plug accesses the rocker-box scavenge oil sump. The rocker sump typically holds around 1 ½ pints of oil or less while the engine main case sump contains about 3 ½ quarts engine oil. Quantities may vary depending on length of time in storage and engine idling (scavenging) time prior to shut-down. The pitch position a counterweight propeller was placed in at shut-down can affect oil levels in the sump.

Here s a tip learned the hard way: Don t take your eyes off of the 5 gallon bucket you re draining that cold 60 weight oil into! It s amazing how large a puddle a gallon of black 60 weight oil will make on a hangar floor!

Pratt & Whitney Service bulletin number 1183, Revision V (Feb. 16, 2005) states that grade 120 is preferred in moderate and warmer climates . Grade 120 is preferred in all engines using dispersant additive type oils except in very cold climates where grade 100 may provide easier starting. We recommend the use of mineral oil for break-in of newly overhauled radials. If you choose to use a multi-grade oil we recommend adhering to the Pratt & Whitney recommendation for using Grade 120 (60 Wt.). If a multi-grade oil designation ends with 60 (IE: 25W60) it is an effective grade 120 oil!

Replacement gaskets for the sump drain plugs, new engine oil screens and check-valve O-rings as well as spin-on filter canisters for the Skytractor Supply and Airwolf filter kits can be purchased at our radial division stock room, speak to Donnie: 918-756-8320,

This series of articles is continued with a segment on Valve Adjustment, Positive Method or Compression.

Fly Safe!
Ron Hollis

Want to talk overhauls or repairs on your engine? Contact David Hamilton at 918-756-8320 or via email: If you would like to discuss the status of your engine, please contact Jonny Oglesby at 918-756-8320 or via email:

What happens if your prop has made contact with something? The standard repair for a prop strike engine is to first remove the crankshaft. The crankshaft will go through two major inspections at this time. The first is a dial indication check (this checks to see if the shaft is bent or twisted). The second is the magnetic particle inspection test (this test is to detected any cracking on the crankshaft). The main bearings will go through the same inspection process as an overhauled unit, with the exception of the thrust bearing. The thrust bearing is automatically rejected because it absorbs much of the shock in a prop strike incident. When the cylinders are removed they have a leak test and AD 99-11-02 is complied with (in accordance with Pratt & Whitney S.B.1787). The blower and rear case section is disassembled so that all the gearing and bearings removed can be inspected, if all is well they will then be magnetic particle inspected. (Note: The R-985 6515 supercharger intermediate gear is automatically rejected per the manual in a sudden stoppage or shock load incident.) The engine case paint is not removed from the cases so only a visual inspection is performed. New gaskets and seals are used in the assembly of the engine. The engine then goes through the same test run procedure as an overhauled engine. The cost to have this inspection done, barring rejected parts, is about 1/3 the cost of an overhaul.

The answer depends on what is needed. If an overhaul is necessary, the answer is roughly 60-90 days. Why 60-90 days? The one factor of the engine overhaul we do not control is plating. It is not uncommon to have, for example, several crankshaft bearing journals that need hard chrome plating to restore the shaft to standard sizing. This process alone is a 3-5 week process. Repairs to the engine have some of the same scheduling challenges as an overhaul. Plating, either cylinder barrel or crankshaft journals, can add to the time needed to repair an engine. A prop-strike inspection can be accomplished in as little as 1-2 weeks. However, if parts need to be plated, processing can add several weeks. We understand that time is not always an option, that is why we do offer exchange parts that are ready for installation. This keeps your engine moving though the repair process and back to you in the fastest time possible.

With over 25,000 square feet of hanger space, we have the equipment, knowledge and tooling to remove and install engines. Please visit our photo gallery to view some of the engine changes and firewall forward restorations we have completed.

The answer is yes. When an engine is disassembled the engine is assigned a work order number that follows the engine throughout its time at our facility. All parts are identified using a metal with the work order stamped into the tag. The tags are only removed when the assembling mechanic begins the build process. Many of the parts as serialized, cases, crankshaft, and cams can provide traceability by serial number. These can be verified by the engine log book or visual inspection. Although logistics does not always make it possible, you are welcome to visit our facility and watch your engine being inspected, built and test ran.

If it’s a 1340 / 985 part we have it! Contact Destry Holiman for parts, manuals, and accessory quotes. 918-756-8320 or email:

Please allow me to offer some information in regard to Pratt & Whitney R-1340 & R-985 engine Time Before Overhaul intervals (TBO’s) for engines utilized on current agricultural aircraft. A letter from Pratt & Whitney (P&W) faxed to the Federal Aviation Administration (F.A.A.) dated February 13, 1990 is useful in understanding the organization’s corporate position on the radial engine.

“Pratt & Whitney have no company or F.A.A approved methods for providing any engineering substantiation or manual/publication revision relating to new methods or procedures which are being accomplished by operators and overhaul shops on Pratt & Whitney reciprocating engines.”

This letter establishes a, “hands off” attitude on P&W’s part concerning the Reciprocating Radial engines. Oil consumption is a major issue and is addressed in a cautionary statement constituting part of the P&W TBO considerations given in the R-1340 & R-985 overhaul manual (part number 123440).

“Oil consumption is usually one of the best indications as to whether or not the engine requires overhaul, provided the engine is performing normally and there is no indication of possible trouble or irregularities requiring more than normal line maintenance attention. A sudden increase of oil consumption or a gradual increase of oil consumption to double that which has previously been average, is usually case for overhaul.”

The engine’s primary accessories (Carburetor, Fuel pump, Magnetos, Starter, Propeller Governor, and Generator) are designed to run to engine TBO. It is our recommendation that they be overhauled at the same TSO as the engine. Ref: AC65-12A Chapter 10 Page 411 Par. Major Overhaul Our basic TBO recommendations are 1000 to 1400 hours operating time since overhaul. In order to determine this “recommended” Time Before Overhaul we have taken into consideration all forms of Agricultural utilization of the R-1340 & R-985 engine and have averaged the operating time between overhauls of engines submitted to us for overhaul over the last 25 years.

It must be noted that there is an Airworthiness Directive 68-09-01 issued to the R-985 engine. It is concerning Crankshaft flyweights and flyweight liner replacement. This AD mandates that it be accomplished at 1200 or 1600 hrs depending on propeller installation. In order to accomplish this, the engine must be disassembled to the point it is more economically feasible to overhaul than to limit to repair and replacement only. This Time Before Overhaul recommendation is made with the assumption that all manufacturers’ recommended/required periodic inspections are complied with in a timely manner throughout the life of the engine. This recommendation is not to certify or guarantee that an operator will achieve a specific number of hours operation time before an overhaul is necessary. This TBO recommendation should in no way be considered a maximum TBO limit as it is possible to safely operate an R-1340 & R-985 past 1200 or 1400 hours TSO. It is merely a RECOMMENDATION that, hopefully, will better enable an operator to develop a safe, economic engine overhaul schedule.