Simple Prop Strikes And Associated Insurance Claims

Simple Prop Strikes: Your Choices And Our Suggestions On Handling The Typical Associated Insurance Claim
Don't Necessarily Take The Quickest Way Out...
The Local or "on the scene" A&P May Not Be Your Best Choice!

"Prop Strikes": What Are They?
Generally a "prop strike" is an event when the prop is spinning via the engine's own power and it comes into contact with anything other than air resulting in visible damage (no matter how slight) to the prop. For the sake of this section, we won't consider a "gear-up" a prop strike even though nearly every gear-up accident involves a prop-strike or more often a "sudden stoppage" event.

When it comes to the common engine manufacturer's language, the engine may or may not have suffered a "sudden stoppage" to qualify the event as a "prop strike". Nearly every "prop strike" event will mean an engine T&I or "tear down and inspection" is required and thus paid for by the insurance company providing you have insurance. In fact, the only variable is whether or not the engine momentum was disturbed, let alone did it come to a complete stop.

Prop Strike Factoids:
Even if the engine doesn't stop or the pilot doesn't even notice it occurred at the time, if the prop comes into contact with anything other than air, the term "prop strike" should apply to the event. Generally speaking, if the damage to the prop is bad enough to be addressed by the examining A&P/IA and/or cause it to be sent out to a prop shop for inspection, repairs, or replacement, the engine will have to be torn down and inspected (T&I).

Read More About It:
For more information on prop strikes, we recommend you read an article in the Jan. '02 "Members Only Issue" of The MOA PILOT Magazine titled: "Prop Strikes Are Just That..." by Charlie Melot, owner of Zephyr Aircraft Engines Inc.

Occasionally the A&P/IA on site may determine that the prop damage was so slight (such as contact with a tie-down rope or chain etc.) that the engine's momentum wasn't appreciably disturbed and that no damage could have occurred to the engine or crank shaft flange area. So, working in concert with the owner they may determine no T&I is necessary. If in doubt, we recommend you consult with the published engine data and/or call the engine service technical rep, OR just do a precautionary T&I as many times (especially with counterbalanced engines) internal engine damage can occur which will only manifest itself later on some hundreds of hours later. Even minor prop strikes can evidence internal damage such as main bearings which tend to shift later on. Crankshafts can fracture, or rods which can be bent etc. to such an extent that when such latent internal damage does occur, it can be causative as to possible catastrophic failures later on.

Years ago before statistical correlation was observed between past prop strikes which didn't result in a T&I, the only criteria was whether or not the crankshaft flange area was bent. Nowadays however, there is far too much statistical data showing a positive correlation and virtually every engine manufacturer requires an exploratory T&I upon a genuine "prop strike" event.

Virtually every manufacturer requires a T&I on sudden stoppage situations, no doubt. In fact, sudden stoppages situations (especially those under power) are a serious situation (engine-wise) and many times internal engine damage will have occurred, especially on engines with sling-type or movable counter-weights on the crankshaft such as the M20J engine. Many times the fear of internal damage is so great that FAA nor the local AI on site will be hesitant signing off a FAA ferry permit for an aircraft which sustained a "sudden stoppage" under significant power.

The engine manufacturers publish well known lists of what is mandated in the form of a required parts list. Make no mistake, a T&I is NOT an engine overhaul or even close. In fact, a typical T&I alone will do nothing to prolong the life of your engine or increase resale value whatsoever.

"Prop Strike:" A Good Time To Consider Your Engine Options
More often than not, a simple "prop strike" will offer the opportunity for the owner to overhaul the engine at a greatly reduced cash outlay. Generally, this makes good sense from an economical standpoint as the bulk of the labor will be covered by the T&I charges which the insurance company will be paying. The rule of thumb is engines which are within the first quarter or first third of the way towards their overhaul period may not be candidates for a overhaul. Most others however, should be overhauled especially those which are beyond the half-way mark to TBO. Example: On a M20's 4 cyl. Lycs, we suggest you consider up-grading a T&I to an overhaul if the SMOH is beyond 900-1,100+/- hrs.

Full OEM Service Manual Spec. O/Haul VS A "Power Section Only" O/Haul:
A "middle of the road" option may be to only overhaul the power core of the engine only and so mark the logs. That is, overhaul the "power section" or basic engine such as crankcase components & cylinders etc., and skip the "bolt-on" accessories (such as: prop governor, alt, starter, hoses, mounts, etc.) which can be done later. This practice is however approaching a "gray area" with the FAA as to if it can actually be termed an "official" overhaul, as the engine manufacturer typically stipulates an overhaul needs to have all accessories overhauled or replaced.
Frankly, we feel most A&P's as well as future owners would recognize a "power section" overhaul for what it is, and that is definitely "counts" in the SMOH consideration, adds value, and can be up-graded later on to a complete overhaul. It is important it not be confused with a true FWF (firewall forward) overhaul which does meet OEM specs for the term "overhaul" or be misrepresented- as such later on.

Picking A Engine Repair Facility:
Who does the T&I or resultant overhaul work and exactly what kind of overhaul is done, (and how it is documented) could very well affect the value of your Mooney long-term. Only in rare circumstances would I recommend you always have the local (incident scene) FBO or shop do the repairs just because the incident happened at their front door. If at all possible, you should consider transporting your prop strike Mooney to the location of a well known engine shop or a "Mooney specific"shop. Sloppy or "botched" T&Is are not uncommon. In fact, once the engine is opened, the owner is tied down to the shop in question as will be faced with many choices and will be in need of good sound council. So, pick your T&I facility carefully. In short, many times a sharp engine shop can actually return an engine in better condition after the incident than before. Many times spending money to up-grade the T&I to full major overhaul at least a "power section" overhaul, is money well spent. In fact, if there ever was an opportunity to spend "smart money" on your Mooney this may be it!

Make no mistake, most insurance carriers will not only allow you to ferry your Mooney to the shop of your choice, but pay for the trip. Some adjusters may be reluctant due to the fact they loose some geographical control (or commissions?) over the job, but and it may be smart to exercise this right in most circumstances. So, unless you have good reasons to leave it where it happens, we strongly suggest you consider putting a "loner" prop on your Mooney, have the crankshaft "dialed" to make sure it will make the trip safely, and fly it to the engine or Mooney specific shop of your choice. As an alternative plan, you can always have the on-site FBO or shop remove the engine and then have the engine itself shipped to the shop of your choice.

Prop Choices: Know All The Facts
Most of the time, true prop strikes will result in both blades being totaled. Once this happens, it is typically just as economical for your insurance company to replace the prop with OEM new. One important fact you need to be mindful of is that typical Mooney prop blades will only suffer a limited number of overhauls before going "out of spec". This is more common with Hartzel props than McCauleys. So, if your blades were relatively new and had good dimensional specs otherwise (generally in the hub areas) and/or perhaps only were overhauled once, we advise you don't blindly accept a overhauled exchange prop for direct replacement unless you know the exact specs (dimensions) of the blades etc. If a "yellow tagged" overhauled but used prop is proposed by the adjuster, have the blades evaluated by the prop shop in writing and compared to your old blades as to if they will sustain any future overhauls. Many times you are better off taking new blades on your hub than a "yellow tagged"overhauled prop of dubious background.
Note: See Dec. '01 Aviation Consumer Magazine for more details.

Often times it is nearly as economical for the insurance company to propose a new three blade prop, perhaps at some slight up-charge. Some industry sources however, have mixed feelings about this as a viable solution for Mooneys if you value all-out cruise or top-end performance. While serious advances have been made with three blade designs recently (Hartzel's Scimitar etc.), generally speaking a typical three blade prop weighs more and doesn't make your Mooney faster... In fact some owners feel they cost them <2-3+/- MPH> in cruise speed. Three blade designs do however seem to change the vibration characteristics to the point they appear quieter in some operational modes. Three blade props also seem to assist in initial take-off roll, but add markedly to drag once the power is taken off such as in a glide. However, even through they don't generally offer speed performance advantages (but possibly hurt speed), many owners elect to have them installed simply from the static esthetic sex appeal. Once you know all the facts, the choice is yours. We suggest you contact other owners of STC'd three blade installations on M20's prior to you making your choice.