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Old 13th May 2012, 09:24
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Genghis the Engineer
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Another of Genghis' thought experiments - the perfect trainer?

Particularly reading the latest of the biannual C152.v.PA38 debates over on Private Flying, I got thinking about training aeroplanes.

Just supposing somebody was prepared to go and put the effort into it, what would make for a perfect new training / school aeroplane?

I'll make a stab at it, and would be interested in anybody else's take on it.

High/Low wing - doesn't matter, whatever falls out of the rest of the design best.

Visibility - Configured for a good view up and behind, as well as the obvious

Seats - Probably 2+2 like the Warrior, which is a reasonable economic balance.

Certification - Part 23 (not VLA) with a basic aerobatic capability, but clearly also capable of being used IMC/night.

Materials - Either semi-monocoque a la C152/C172/PA28, or metal frame + lightweight skin a la C42. As an engineer, I rather favour the latter, which is much easier to inspect, maintain, and repair. Keep the composites to secondary and tertiary structure, and the volume of it down to avoid it putting weight on parked outdoors.

Cockpit layout - Probably both glass (LHS of panel) + standard analogue (centre of panel). That way most instructor parallax is eliminated, and both are available for training (or for turning off!). On which subject, design it straight off with the ability to blank or fail instruments, which is easy enough to do. Good wide wrap-around panel with lots of space for future avionics that nobody's invented yet. Include a centre console between the seats for e.g. radios, it makes it "airlinerish", gives a bit more elbow room, and also allows the coaming to be dropped and thus a better view out.

Flaps - mechanical, PA28 style. Electric flaps don't add much.

Gear? - Hmm, here I propose to be radical. It is quite possible to design an aeroplane from the off that can be configured both with nose and tailgear. The most obvious example is the Escapade. So we get two aeroplanes in one. Do we want retractable gear? Difficult - only really useful for CPL training, since most other people don't really want it. I'm going with fixed gear, but make sure that the design incorporates the ability to put a retractable gear on later models fairly easily.

Engine - Hmm, a minefield. The choice is basically 912 or Lycontinental, since nothing else really has the worldwide maintenance support. I'm going to propose a fuel injected 912, but with a mixture control. Plenty of maintenance support, cheap, economical, and not prone to carb ice (mind you, neither was the carburated one!).

Doors. Let's be really radical and let everybody have one! Okay, let's say 3 doors for a bit of simplification.

Handling - positive spiral stability, but not to strong, pull force to stall of about 8-10 lbf, strong lateral stability (that's easy with the positive spiral stability) and a weakish rudder to ensure that pilots have to use their feet. Design for a moderate pitch-up with flaps, and a moderate, but not excessive classical pitch up with power. Spring pitch trimmer on a lever or wheel, with a well placed indicator. Yaw trimmer, probably in the roof; put that on a tab so students learn about both types of system. Design a wing that gives good pre-stall buffet, but also add in an audio warning - again so students can learn about both. Try and design for a bit of wing drop at the stall and a sharpish pitch break.

W&CG. Design for a wide CG range, then publish a slightly narrower one that forces students to do the calcs. Empty weight good for 2 x 100kg adults + 3 hours fuel.


This would all actually be quite easy to do.

Any thoughts?

G
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