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Diyguy

'Trigger' altimeter?

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Wondering if anyone is familiar with a type of altimeter which can be preset to trigger something-switch, circuit-at a predetermined altitude. I was doing some research on the 1930's vintage Ju 87 'Stucka' which purportedly had an 'automatic flight assistance system' ,using a "contact altimeter", to trigger an 'up' response which pulled the plane out of a dive if the pilot blacked out. I read of a laser altimeter used by NASA, but the 30's era technology must have used a fairly low tech solution. The point is, I was wondering how you could replicate this action in a model. Any thoughts?

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'Up' elevator! I have a short kit of the Ziroli 'Stuka' and would like to incorporate the 'automatic pull-up' feature. Apparently the "contact altimeter" was set at 1475 feet which initiated the sequence, pulling the plane out of the dive. The pilot, as I understand it, pushed a button when he commenced his dive, this engaged the dive brakes, etc., the rest of the maneuver was carried out through visual observation of gradients painted on the window.

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http://www.tvnsp.org/modules.php?set_album...=view_album.php

This is a small capsule I built last yearwith some external ballistics in mind. We launched it under a weather balloon to 93,000 feet MSL. I commanded it to drop via DTMF decoder. It fell exceeding 366 mph to the Southern Idaho Desert. I used a BS2 , (Parallax Basic Stamp 2) microcontroller to watch GPS altitude information. Once the capsule passed through 20,000 feet MSL it deployed the chute to land. The ground was 5,000 feet MSL so I still had plenty of drift. It sounds like this is what you want to do.

In your application though I would use something like an OEM GPS 18 with WAAS enabled. You need to account for time it takes for the GPS to feed out it's serial data and the program to pick it out and send a signal to the device that causes the pull out to occur. You also have to program the Basic Stamp at each field to account for the AGL altitude you want to pull out.

Just an idea. There has to be other equipment and PIC chips with code that can do the job.

Dan

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Thanks for the thoughts. Had not thought about using GPS data, but think your right about the time delay. For a model to do this in a scale like fashion, it would have to 'pull up' at about 150-200' to be realistic. I guess one could use a Futaba PAL or FMA Co-pilot to accomplish the appearance. That would call for a judgment at the proper time. Interesting to me the Germans could figure this out in the 1930's with no electronics to speak of! 93000' drop, that's impressive!

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I think barometric sensing that you can calibrate to the field altitude before flight would give you the best and most accurate response. But I think there's less off the shelf for that. It's a more Do it yourself project.

I did happen to notice the GPS 18 now comes in a 5 Hz model. The original one was 1 second. Although 1 second was fine for me it would be abysmally slow in your high speed application.

Good luck. It sounds like an advanced project.

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Hi, Diyguy

This "scale" feature looks pretty :D ... but :

- our planes will begin to dive at a much lower altitude to permit the public to see something ... so ground will come much faster than for original plane.

- as the Ju 87 is not really a pattern model, it will need some altitude loss to get quietly back to horizontal flight.

Those two points make me think you won't have a lot of diving attitude to show ... may be very little time to hear the famous diving sound of the hooter.

Another point to raise is for pressure inside the fuselage : as speed is not negligible, which will be the speed effect ? : important point, as you set the diving stop altitude on the theoretical pressure for altitude ... :unsure:

Your thinking ?

Alain

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Short answer, Alain, I don't know. First of all, I have yet to determine what a 'contact altimeter' (used in the original) is, or was, thereby ruling that in, or out. I would assume full sized aircraft had, or have, the same problem and I assume use an external pitot to 'read' the pressure. The much reduced altitude differential-say from 500' down to 150'- doesn't leave much room for error. The hackable sonar devices, like a Polaroid camera, I don't think would work 150-200' up. A laser altimeter device is beyond me. I'm not sure a WAAS enabled gps would give a quick enough response time either-perhaps from 5000' down to 1475' it might work (apparently 1475' was the altitude used in the original Ju87, though I think that must have relative to a particular geographical area-wouldn't be much help diving into a mountain 5000' high).

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:huh: ...Hi guys... A different approach will be to look at the parachute-way to do things... I think it must "work" the same way than the stuka system. When you are a beginner to parachute dive (the real one), you have a neat little device velcroed on the top uf your right shoulder strap that will open your second parachute (the security one) automatically.That thing is a little 2 cubic inches black plastic box with a graduated adjustment screw in it, and it HAVE to be effective and VERY reliable, since it must open your chute in case of "brain power failure" when you dive. It does his job only if you pass the threshold altitude faster than at a predetermined speed (unknown to me).

And the alt is adjustable, so i think you should look in that direction if wou want to keep the thing as simple as possible since it's as entirely mechanical device.

Hope it'll help, 'cause your project seems very cool... :rolleyes:

Ciao.

Soulglow.

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That, Soulglow, is a nifty idea! I'll have to research that device. Do you happen to know what it is called? I had looked at some skydiving sites looking at altimeters, but didn't see that device mentioned. Bill S.

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