When I purchased my B55 i knew it had damage history related to a prop strike when the aircraft took a short cut to the taxiway and dropped a wheel . The engine was removed disassembled ,xrayed , magnafluxed , and reassembled . The prop was repaired accordingly. The event happened 8 years ago . Most people in the know say the time distance between the event and the sale is an important factor in diminishing the impact of damage history devaluation and of course the type and extent of damage is more important .
The question I have is how do you measure or apply a percentage drop given all factors ? What was the damage, how long ago , who did the work.

In my case with an airplane costing less than $170k and how nice the airplane was at the time of purchase and still is ,and with all of the other great amenities (low time airframe ,engines , great avionics) I did not consider it important to make a big issue of the previous damage history. There were several other buyers seriously considering the airplane at the time ,so I assume I wasn't the only one not too particularly bothered .

The reason I am asking after the fact is that I am looking at a 421C which has all the things a buyer would like to have but has had extensive damage history 20 years ago.The asking price does not even consider that the aircraft had any damage history. What percentage drop would you assign to an aircraft which had a runway departure on takeoff and slid out thru a snow covered field ?

20 years ago? All repaired appropriately and no problems with the repairs in the 20 years since then? That wouldn't matter to me at all.

BUT, when you try to sell this plane, there are some potential buyers who won't consider it because of the damage history, and so it may not be as easy to sell, and so the selling price may take a hit of a few percent. How much? It's whatever the market will dictate at that time. There's no magic formula.

20 years ago with the only damage to the prop and engine, which was subsequently repaired?

I wouldn't subtract a single penny.

Jason

Yup, not a thin dime.

Honestly, these airplanes are almost all getting to be 40+ years old. If anyone has been flying them, they've all had at least a little damage history unless they've been sitting in a hangar the whole time. When you consider the low prices on most of these birds these days, where would you even go from here? Free?

Forget it. Not a thin dime if the repair was done correctly and more than 10 years ago in my opinion.

I personally don't consider damage to removable wear parts such as wheels, props and motors damage history.

On your B55 with only a prop strike and proper repairs, as the others have said I'd deduct exactly nothing, just like I'd deduct nothing for an airplane that had blown an engine and has a new engine installed. That repair has solved the problem. (Casey said it best, after I started typing my reply. I agree 100% with that.)

My 182 has damage history 3 times in its past, all properly repaired, and it may take a slight haircut on price when I sell it, but as Craig said, a lot of these airplanes got pranged at some point. I had no problem buying the airplane with that history.

Where I diverge from the others is on the 421 part of your question:
On a 421C that did some impromptu agricultural work, resulting in "extensive damage", I either wouldn't consider it, or would discount the price I was willing to offer by at least 25% of the basic airplane value. (You can't discount 2011 avionics or 2005 engines for 1995 damage history of course.) There are enough clean 421s out there and they sell slowly enough, that I don't see any reason to pay full sticker for a plane with extensive DH, because you can't reasonably know that the airframe is completely repaired AND because it will attract a smaller pool of buyers when it's time for you to sell.

I'll buy and have bought DH airplanes (IOW, I'm not one of those "she better be perfect" types). Even I'd think twice about that 421 (based only on your description of extensive damage), so it's not going to fetch as much at resale, so you can't pay as much now, since resale is an important part of the value proposition.

In all likelihood, it's a safe and fine airplane if it's been flying 20 years since repairs, of course.

I'm with Jim. I've bought and sold two airplanes with damage history. Both were great aircraft. Buying them was easy and selling them was hard. There are a lot fewer buyers who will consider a damaged history airplane in my experience and fewer still who will buy one. They all want a discount. So, the PITA factor, not to mention the reduction in value these buyers demand, require a very gimlet eyed appraisal. There are an increasing number, or should be based on pilot and hours flown decreases in these airplanes. There will be more non damage history planes to choose from in the future than there are today which will exacerbate the issue.

If you're going to fly this airplane forever or part it out when you're done with it it doesn't matter of course.

Damage history (not a salvage rebuild) well repaired with strong maintenance and regular replacement of key parts (bladders, reskinned control surfaces, seals, gears, motors and pumps)... I'd take that all day, every day, compared to a NDH hangar queen with rotten guts from cheap maintenance. Sure you may pay a bit less and you will likely sell it at a similar discount. It will be a wash. Yes there may be some buyers who won't take a look.
Nevertheless an updated aircraft that is impeccably maintained will sell quickly and at a good price even with a gear up history or some hangar rash.

DH well repaired and hours on the Hobbes is a non issue for me. My Archer had an over run off the runway and a wing replacement. I paid fair market value and no discount for a taboo mark on its MX logs.

A proper, well documented repair has no actual valuation penalty. But, some buyers think a 337 in the logs is going to drive it to salvage value.

The problem with "damage history" is scars that can never be repaired. Airframe problems. Prop strike isn't damage history.

Agree with Jim regarding 421 DH. Airframe offroading is a different issue. I agree 25% hit on value of airframe (distinct from cosmetics, avionics, engines, props) is prob appropriate.