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Buying an Aircraft - What do we look for?

We don't just spend all day selling aircraft, it is rare that a day goes by when we don’t consider buying something either for resale or to part out. We’ll leave the parting out side of things to the experts, and just consider potential flying aircraft here. So armed with a torch and a Phillips No. 2 screwdriver we set off to look at two Cessna 172’s last week and bought the less obvious one of the pair. Here are the items we considered in making that choice. 

10 point inspection plan

1) Corrosion proofing. Simply put corrosion proofing is either applied at manufacture or not, and it can make a big difference to the life cycle of an aircraft. Open an inspection panel and if its uniform light green or yellow inside then you have factory corrosion proofing. Pipers, Reims and some American Cessna’s have it. No corrosion proofing should trigger a closer inspection for snow like deposits inside wings, flight controls and the fuselage.

2) Logbooks & Documents. Having full logbooks back to birth is a big factor if you are changing the state of registry of the aircraft. If there are missing historical logbooks this can be reflected in the price, provided the most recent logs are present. If there are no logbooks at all, then it is not a job for an amateur!

3) VAT. There are very few aircraft that will have proof of being VAT paid in our experience. Thankfully EU transitional measures mean that there is no VAT-able event in most light aircraft sales. Where you need to watch out, is in cases where the current owner and previous owner were both limited companies, in this case VAT will most likely be payable. Another VAT trap worth pointing out is, if you import an aircraft onto the EI register you get a free Revenue audit, which can ruin your year. Think very very carefully about this and get some good advice.

4) Ferry Permits. An aircraft out of ARC or Annual can be moved via a Ferry Permit. It will need to have all AD’s up to date and at least have the equivalent of a 50hr check. The relevant document on the IAA website is Aeronautical Notice A.91 and the CAA have similar procedures.

5) Payment. Payment will either be by EFT or counted cash. A bank draft with a receipt will work on a week day but expect to be asked for it to be presented in the bank before you will get possession. 

The next event is getting onto a look at the aircraft itself….

6) The engine is the life of the aircraft so it makes sense to start there. You want the engine to do a couple of things.

  1. Hold oil pressure when warm at idle
  2. Have strong compressions in each cylinder
  3. Not make metal while doing A or B!

So with that in mind you will ideally fly the aircraft for 30 minutes. Recommendation is to climb at full power, checking the rate of climb from 500ft to 3000ft with a watch. Then a clean stall with the ball centred will tell you if the aircraft is rigged correctly. In the cruise trimmed out watch for what control inputs are required to hold a heading, wings level with the ball centred.

The amount of input required tells a long story about the rigging. A Cessna can be rigged for about €700 using the Cessna Pilots Association rigging procedures, so rigging is only like tracking in a car to that end. In flight check all Coms, Navs, ADF, GPS, DME and Autopilot for functionally aloft. If the oil pressure at idle at the end of the flight is in the green then its time to move the inspection along.

7) We’ll look in the engine bay now, so its time to get a compressed air source and measure the compression of each cylinder with the results being expressed as XY over 80. Think of it as an exam result being marked out of 80. Many consider 60/80 to be the pass mark here. Lower numbers can occur with Continental engines and Continental say an engine can still produce full power at 20/80 - so lower numbers may not necessarily be fatal.

If you have a new oil filter available, then we would remove the old one and cut it open to inspect the screen for metal. Replace with a new oil filter topping off the oil level, and record same in the logs.

8) Before putting the cowlings back on, look for oil leaks around cylinder bases. Then look at the condition of hoses, the condition of the battery box and the straightness of the firewall. Engine mounts should be looked at closely, and then the propeller. The prop should have a uniform leading edge. There should be no corrosion on the prop and ideally you should track the prop over an heavy object. If the prop does not track within limits it is time to go home….

9) With the engine cowled up its time to look at the airframe. Open the inspection panels, putting screws in the holes they came from, and take a good look inside. Obvious thing to look for is white corrosion deposits, but also the condition of cables/pulleys and bellcranks. The amount of lubrication on them is a good give away along with the cleanliness of underfloor panels.

If the horizontal stabiliser is all moving, then grab it by the ends to rock it side to side and up and down. Correcting any play here is very important. Similar play in the flight controls could be detected by having someone hold the controls firmly and moving each surface. The remedy is often not expensive, but it is not going to fix itself!

10) Now with the log books open, put them in three piles (Airframe, Engine & Prop). Fixed pitch propellers will not have a logbook by the way, as they use the engine log book. Then record the start and stop date of each book looking for gaps. Look for the most recent engine overhaul and prop overhaul EASA Form 1 or FAA Export 8130-1 as they are really important to have.

The last annual is a good clue as to how much or how little work the aircraft needed at that time to be airworthy. The pink pages in the log books record the Airworthiness Directives. Not many can read AD’s accurately, its a black art, but it is well worth doing with a current AD print off from the FAA website and checking them off one by one. There should be a time life component sheet for an EU registered aircraft (See CAP 543 if its a UK aircraft) and this will typically be completed by the maintenance organisation which is a forecast of inspection tasks and time life limited parts.

This is important to review, but bear in mind for aircraft under 1999kgs MTOW the EASA regulation on ELA1 and ELA2 (which is coming in 2016) makes the tasks and component lives a lot more flexible and gives room for things to be assessed on condition rather than on strict time or hour limits. On a UK reg aircraft the engine must be less than 14.4 years old for the aircraft to work in a flight school, and for an Irish reg aircraft this is slightly longer at 20 years. For private use the engine can carry on, provided it is in good condition, for an unlimited time on both hours and calendar time.

So there you have a brief, but quite respectable checklist of the vital signs you need to see when you are buying an aircraft. If your proposed purchase scores well in all these areas chances are it will do the job quite nicely and you will have no problem when it comes to trading up to that Cirrus SR22 you’ve been promising yourself!


William Flood
William Flood

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