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Another of Genghis' thought experiments - the perfect trainer?

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Another of Genghis' thought experiments - the perfect trainer?

Old 13th May 2012, 10:24
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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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Old 13th May 2012, 10:28
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I'm not very experienced with my training so far so unable to add anything very constructive, but I would say wide enough so you don't constantly crash elbows with your instructor!

Last edited by average-punter; 13th May 2012 at 10:29.
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Old 13th May 2012, 11:08
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'India-Mike
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Ah Genghis, ever the engineer!

Let me look at it another way...

So long as it uses less than 5 IG/hour, can run on cheaper stuff than Avgas, has an endurance of at least 3.5 hours and can lift two 89kg people without restriction - I'd be happy as an owner or a student pilot. I don't necessarily mind continuing to train on old aeroplanes but I wonder why some places do so at 8USG/hour

The engineer in me would like all the fancy aeronautics and systems stuff as well though.

In terms of handling/space/fuel economy...something like a Beagle Pup 100. But with no payload/fuel restrictions and more performance. It's a real nosewheel Chipmunk.
 
Old 13th May 2012, 11:57
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Just some thoughts

I wouldn't go for the fancy panel just your straight 6 plus an AH on the instructors side. VOR/ILS and a panel mount GPS. With Two VHF's which are stand alone and not linked to the GPS. You can have a fancy engine panel if you so wish. Although a big screen which could display the 6 then be easy configure for EFIS style would be acceptable and being able to turn off individual instruments of the 6 would be a bonus.

The controls would also be designed for hand rudders/brakes etc to be easy fitted without and engineering sign off.

Power plant as per IM.

Metal skin please for the aircraft nice and easy to fix as you say.

Design

2 doors
low tail
low wing
Trimming a proper trim tab on the elevator.
Certified to Spin.
Limited aero's but nothing special.
Sprung steel gear like the PA38 and C152. Large tyres, hydralic foot brakes.
Tail dragger option would be nice.
Cockpit ergonmics similar to PA38 but different door design.

Engine compartment must be able to get a good look at the important bits including being able to get at the plugs with out having to take the cowlings off.

Led landing lights.

12V power supply in cockpit.

And a removable rumble strip on the leading edges. ie so when you are teaching stalling you get tons of buffet over 5 knots to prove a point the rest of the time its normal.

Face level ram air fresh air vents.

Footwell air vents/ hot air ducts. (Its important to have both so you can heat the plane but also get fresh cold air in the punters face)

I shall think some more though and add.
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Old 13th May 2012, 14:06
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What about the choice between stick or control wheel. Definite preference for a stick and left hand throttle as I find it much more natural to use - probably since it is what I first trained with. Maybe stick on the tailwheel version and wheel on the nosewheel version.
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Old 13th May 2012, 14:42
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Don't mind either way to be honest.

But stick on the tail wheel and yoke on the tri seems as good a plan as any.

I really do think though that anything should already have some thought put into mods for disabled pilots from the beginning. If you put a very small amount of thought into it before testing adding in say an extra control port on a master cylinder for example it means that that things can be jigged for individuals easily.

And don't think that disabled pilots are a small group with limited appeal.

To put it bluntly its a market with quite a bit of cash in it if you put the effort in to allow that market to access your aircraft. Just now though its bloody expensive for the mods and most schools won't put the effort into getting the plane sorted. If there were kits that come pre-approved through the intial certification testing it would make life a whole heap easier.
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Old 13th May 2012, 15:13
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It sounds awfully like you're trying to reinvent the Beagle Pup 150!

Industry survey had identified a significant demand for a light 2/4 seat aircraft with good all-round flying and aerobatic characteristics to replace the ageing aircraft in use by flying clubs of the time, so Beagle decided to design an aircraft to meet this need. The required characteristics were for an all-metal low-wing monoplane with side-by-side seating in a wide cabin, with plenty of elbow room and easy access from each side. The new aircraft was required to possess good performance and rate of climb with faultless stability and manoeuvre characteristics and to be capable of unrestricted spinning and aerobatics within the semi-aerobatic category. It was also to have first-class ground handling and to be very reliable with ease of servicing and maintenance a high priority.

In response to these demanding criteria, Beagle designed the B.121 Pup, which first flew in 1967 with a 100 hp Rolls-Royce Continental engine as the Series 1 or Pup 100. It was soon followed by the Series 2 or Pup 150 with a 150 hp Lycoming. A small number of Series 3 or Pup 160 aircraft fitted with a 160 hp Lycoming were later built in response to an Iranian civil training requirement. A total of 173 Pups were built, 66 Pup 100s, 98 Pup 150s and 9 Pup 160s; when production ceased, a significant number of additional aircraft were still on the company’s order book.

Last edited by BEagle; 13th May 2012 at 15:14.
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Old 13th May 2012, 17:13
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A cross between a Grumman AA5 & Grob 115 would be quite close I reckon

Other things I'd like -

Some kind of quick change landing light or LED like MJ says
A least a few 12V power sockets
Car like seat belts like I think Cirus have (unless you need aeros harness I suppose)
Some kind of TCAS, have flown with the one in the Tutor and ought it was really useful
Fuel tanks that you can easily visual check with some kind of graduated scale
Checklist integrated into any glass screen display
ISOFIX so people can take kids flying perhaps?
 
Old 13th May 2012, 17:18
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Originally Posted by BEagle View Post
It sounds awfully like you're trying to reinvent the Beagle Pup 150!
A wonderful airplane hopelessly over engineered resulting in the company losing money on everyone they built. The economics are just as important as the flying qualities. The flying club I joined is still operating the the same 2 bought new C 152's they had when I joined in 1979. they both have over 17,000 hours now and are still going strong. The C 152 has plenty of faults but it is has never been equaled as a robust and cheap to operate and maintain trainer.

One thing is for sure the LSA airplanes are a dead end.

Last edited by Big Pistons Forever; 13th May 2012 at 19:48.
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Old 13th May 2012, 19:31
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Revised and updated PA-38 powered by a Rotax and approved for mogas with 10% ethanol.
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Old 13th May 2012, 19:37
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There's an updated Aussie PA38 with a low tail but otherwise identical. An up to date version with a more economical engine (not necessarily the rotax!) and perhaps a revised W+B schedule would be ideal.

Basically for it to be a good trainer, it needs to be a reasonable handling beast but should be quite stable in pitch relative to the current LSAs that are quite twitchy in pitch. Light on fuel, the 0-235 is actually pretty good at this, it will almost certainly take UL91 if it's not already cleared for it but the new lightweight conti 0-200 would be a better engine than the rotax for the job of a trainer, I don't believe that reduction gearing is up to the constant hamfisted power changes required for a trainer.

But it just has to be tough, inside and especially the gear. It needs to put up with 800 hours a year of which 600 are circuits. Simple is the key.

Aeros would make it too expensive because the certification process will be more complicated. The simpler the better.

Last edited by Dan the weegie; 13th May 2012 at 19:51.
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Old 13th May 2012, 19:55
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I've heard they went bust. Build quality was shite and it was still powered by a gas guzzerling 235

A Rotax is good for at least 3 thousand hours and burns less fuel than a 0200 or 235 and no 'top end' overall either.

Last edited by Mickey Kaye; 13th May 2012 at 20:53.
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Old 13th May 2012, 20:16
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Genghis - you should write this up for one of the pilot mags
 
Old 13th May 2012, 21:30
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The problem with rotax is that nobody up north will touch them for servicing and you need to have mogas on the field.
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Old 13th May 2012, 22:27
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Some great thoughts here, a few thoughts back:

- I appreciate that some parts of the world don't trust the Rotax product. Simple solution, add into the aircraft options two powerplants - a Continental and a 912. Let the market sort it out. An expensive hobby, but at the same time it creates an insurance policy for people either side of the fence and may help sales.

- I prefer a stick as well. For me. What about for a training aeroplane however, which was my question? Are there real advantages to a stick in a trainer?


And some questions back at Blagger in particular:

Some kind of quick change landing light or LED like MJ says
Damned good idea, and very easy.

A least a few 12V power sockets
Absolutely! I think myself I'd go for USB sockets rather than the horrible wobbly cigar lighter style that we're afflicted with still.

Car like seat belts like I think Cirus have (unless you need aeros harness I suppose)
Hmmm. I grew up on military aeroplanes then 3-axis microlights, both of which normally had 4 point harnesses. I can see why a car style makes good sense if you prefer to have a 3-pointer but, dammit, I like a 4 point harness. What does everybody else think?


Some kind of TCAS, have flown with the one in the Tutor and ought it was really useful
Hmmm again. In a trainer? Teach technology dependence early on? I'm unconvinced.


Fuel tanks that you can easily visual check with some kind of graduated scale
Like 2 of the 3 aeroplane types I've flown in the last 3 days. Strangely these two were microlights - it's dead easy to do, and I agree utterly. Why does the group A world have such a hatred of the wonderfully simple sight tube?


Checklist integrated into any glass screen display
Hmmm yet again. It's still a training aeroplane - training pilots who mostly will go onto fly aeroplanes with paper checklists. Have a go at convincing me, but you've not done yet.


ISOFIX so people can take kids flying perhaps?
Any instructors here keen on flying students who have their infant child in the backseat?

Again, perhaps a nice idea for a GA tourer - but my question was about a training aeroplane.

G
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Old 13th May 2012, 22:40
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Originally Posted by Mad Jock
2 doors
Or more

low tail
Why?

low wing
Why? A high wing doesn't have to have a crap view into the turn - my 1947 Stinson has the wing far enough behind the cockpit it's fine, and plenty of high wings have windows in the roof. (I like high wing too, but I'm trying to bottom out the argument for a training aeroplane.)

I do really really want a window in the back of the cabin however.



Trimming a proper trim tab on the elevator.
Why, rather than a spring?

Certified to Spin.
I agree, although I'd probably only certify to 4 turns, erect, or the certification costs get seriously painful.

Limited aero's but nothing special.
I agree. The Auster with +4.5/-2, and clearance for spins, loops, stall turns, and the usual derivative manoeuvres, seems an adequate model.


Sprung steel gear like the PA38 and C152. Large tyres, hydraulic foot brakes.
I agree on all counts (although composite leafsprings can work well too).


Tail dragger option would be nice.
And fairly straightforward.

Cockpit ergonomics similar to the PA38 but different door design.
I agree, very much one of my favourite cockpits as well.


I also like your idea of an EFIS screen switchable between "6-pack" and "Garmin", a straightforward and easy solution to a problem. Shove an analogue ASI and Altimeter in front of the instructor for their use, and as a backup and that should work quite well.

G
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Old 13th May 2012, 23:45
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A spring is shite and allows the plane to hunt more in turbulence. It also relaxes over time and the dog clutches are a pain in the arse when they get old and are expensive and a pain to fix. Trim tab stays put and doesn't suddenly dump the whole lot of tension when it gets on a bit.

Low tail so you can teach performance and grass field departures with prop wash going over it. And so folk don't moan about the tail waggling when you spin it. Also helps with teaching secondary effects of controls.

Low wing so its easy to see into the fuel tank, and also its easier to get folk down into the aircraft if they are a bit dodgy than up and through while balancing on a step on the leg. Once you have done a load of trial flights you will know where I coming from. If its high wing all the auld buggers won't go up and check the tanks if nobody is watching. Also the pie eaters won't either. I have seen more than a few skinned chins climbing up to look in C152 tanks. Again you have problems getting disabled pilots signed off if they can't do a full walk round including looking in the tanks.

O and the fuel gauge is floats in the tank which change colour of a disk on the wing when the fuel gets below that point.

O and the tail of the 2/4 seater has to be strong enough to pull gliders. And it has to be certified to fly with the doors off as well.

As for stick or not. Personally I don't think it makes much difference. But either way have modular design to allow the PTT to be plug and play swapable without any soldering or fannying about. Also a back up PTT next to the power lever with a cover on it that isolates the others for when the inevitable happens.

The sprung steel works and takes some serious abuse. Leaf springs do wear as any old land rover owner will tell you. KISS i think for that choice.

And TCAS wouldn't be such a bad idea to be honest these days but have it on a set distance display 5 miles and no up down modes. And big sign above it with "nobody cares if you can see traffic on this display"

O and 4 point harness please but with the ability to disconnect the shoulder straps without releasing the lap straps. No intertia reels they are the same as the dog clutches a right PIA and expensive when they go wrong. Although you could add them as an option.

Last edited by mad_jock; 14th May 2012 at 09:30.
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Old 14th May 2012, 01:18
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Viz-Good
Seats-2+2
Cert-Not VLA
Materials-Metal frame lightweight skin
Flaps-Mechanical,
Doors-3,
Trim-mechanical wheel
Yaw trim tab

Sounds like your describing my Maule MX-7
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Old 14th May 2012, 10:49
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Thanks Jock, now I'm going to challenge you a bit. I was trained when I learned the fine art of flight test not to say "this needs more dihedral" but to say "this needs increased lateral stability". The difference being that in the first you are owning the solution, but in the second you are owning the problem. The difference is that it's okay getting the blame for telling everybody something is wrong with the aeroplane, and what - but if you tell them what to do to it, and you are wrong, you'll get it in the neck.

Plus test pilots test, and aircraft designers design. (Although test pilots may point out what designs have worked fine before.)

What I want to get to is the problems, so it seems to me that what you are really saying is:

- An aeroplane that can be fuelled, and the fuel checked visually, without climbing on anything, and the latter ideally whilst strapped in.
- Front seats that can be easily accessed, again without climbing, and ideally from a wheelchair.
- Easy and direct entry and egress to most of the seats, and definitely the front left.
- A firm, non-slipping, pitch trimmer.
- A rugged, maintenance free, undercarriage which isn't prone to corrosion.
- PTT disable and backup.
- Tail positioned to make prop-wash effects happen.
- Full harness, reconfigurable to lapstrap only, with simple operation and adjustment.

?

G
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Old 14th May 2012, 11:45
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The fuel check is more of a pre flight belt and braces check to confirm what the gauges are saying even the optical ones can get blocked with crap. It needs as folk have been saying to be able to look in the tank and see calibration marks a bit like the cross in the tommy tank to gauge how much you have. None off this poking shitty sticks into it and then hoping who ever made the stick up got it right. Apart from anything else you end up with a impregnated with petrol fire hazard on the plane never mind running the risk of contaminating the tank.

The access thing may seem daft to the majority of PPL's but when you have a full range of mobility of punters turning up it can make a huge difference to how much aof PIA it is getting them loaded. The tommy/PA28 with the help of a carvan step is great nice wide walk way, door frame to grab onto. Then once they are next to the door they have a small lip to get there leg over before going down. To be honest you would be better talking to the disabled flying club. The PA38 is a bit to much of a step down, the PA28 is better but its suffers the problem that they have to shuffle there backside over once they are in. The cessna's its becomes more intimate with hands on bottoms and hefty shoves to get them loaded. Best way again is a step then get them to sit backwards then swivel round in the C172 but The C150/C150's the seat doesn't go back far enough and your head is banging off the wing.

On the matter of bits to grab you need good solid obvious grab points. If its in front of the punter they will grab it and put thier full weight on it. If you have designed something that is grabbable but you haven't designed it to have a 110kg bloke pulling on it its only a matter of time before it gets broken.

Not to bothered about having more than two doors on the 4 seater three would be nice. But you definately need a two seater option. No point taking an extra two seats of weight with you for 80% of of your flying.

Pitch trimmer

under carrage you have it with no spats or any of that crap and a jacking point thats works with a car jack. And if possibly even a tempory get it off the runway attachment point for a castor. And the nose gear needs to be a meaty job with good prop clearance when flat and that flat tyre and when the seals have gone on the gas combined.

PTT pain in the backside getting them fixed. Sacraffical socket would be a better way of putting it with the PTT modual swappable without resorting to using any tools apart from maybe a philips to release the modual. The modual so shaped it can only go in one way.

Tail

Full harness for depature and landing but allows you to disconnect the shoulders in the air to get to the back etc.

Last edited by mad_jock; 14th May 2012 at 12:00.
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