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Three Tips for an Effective Aircraft Evaluation

by David Wyndham 1. March 2010 00:00
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Buying on impulse often leaves you disappointed. What looked or sounded great in the moment can turn out not to be what you thought you were getting. This applies to love and fast machines. With aircraft, it then applies double!

The first tip when looking at what aircraft to acquire is to be objective. Objective means choosing criteria that can be measured. In this way you avoid the subjective trap: what was great last night can be less than desirable come morning. With objective criteria, you can compare more than two aircraft and rank order them. Be as specific as possible. Non-stop to West Palm Beach is good. Non-stop to West Palm Beach with four passengers is better. Non-stop to West Palm Beach with four passengers, IFR fuel reserves against a 25 knot headwind is best. If what you are measuring isn't in units of some kind, it's doubtful that it is objective. The joy of an aircraft used for transportation is in proportion to its utility.

Objective criteria should also be specific to the mission assigned to the aircraft. That way you can avoid over-buying - getting far too much aircraft than you really need. If you are clear about what you need, it is easier to set up your criteria. "Go anywhere, anytime" might set you up for a supersonic tilt-rotor amphibian, but can you afford that?

The second tip is to separate your criteria into desired and required criteria. Required criteria are criteria that the aircraft must meet in order to do the mission (job) assigned to it. If the aircraft does not meet the required criteria, it should not be considered any further.

Desired criteria are those that enhance or expand the capability of the aircraft to perform its mission. Generally speaking desired criteria go beyond the minimum needed for the mission, or perhaps they make accomplishing the mission easier, or faster. Once you have your aircraft that meet the required criteria, you can use the desired criteria to differentiate between them. This is helpful in rank ordering the aircraft. Here is a basic example:

Mission Criteria

Range with 4 passengers (NBAA IFR Reserves 200 NM)

1,800 NM
2,100 NM

Range with 6 passengers (NBAA IFR Reserves 200 NM)

1,500 NM
2,100 NM
Passenger Seats
Hot food galley?
Convection Oven

If you understand your mission, then you can your criteria to reflect what you need to do, and also choose desirable criteria that are meaningful. In the above example, the aircraft buyer was OK stopping for fuel on the 2,100 NM trip, but not for 1,800 NM trip with 4 passengers, of which there were quite a few.

The third tip is to prioritize before you analyze. If you group your criteria into sub groups, then you can not only rank order within those sub groups, but also prioritize which sub groups are more important. Again, this is best shown in the below example. Do you value more range over a bigger cabin?

Mission Score:
Range 60%
Cabin 15%
Payload 15%
Speed 10%

In this case, once an aircraft meets the required cabin size, an aircraft with a larger cabin has value, but not a lot. But, once an aircraft meets the required range, additional range will be greatly valued. This can be done once again after looking at the costs and supportability:

Total Score:
Mission 50%
Life Cycle Cost 35%
Product Support 15%

Here, an aircraft that costs a little more but offers more capability may be the best ranked aircraft in the group.

A big caveat: set this up before evaluating your aircraft. If you really, really want that supersonic tilt-rotor amphibian, you may ignore the fact that you really don't need to land on the water! OK, a bit of a stretch there but the warning is to set the rules first and then perform the evaluation second. What is important to have in your aircraft?

All of this can help you identify the "Best Value Aircraft." We do a lot of our work on the cost side, but we always stress that a large gain in performance at a small increase in cost may be well worth the added expense. At the end of the analysis, it is the responsibility of the decision maker (the one who writes the check) to arrive at that best value. An objective analysis should be done first.

Have you had any experience with this topic? If so, Discuss it with us by clicking "Reply"

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David Wyndham


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