Aerobatic Autopilot

[TheGorrilla]

There's a few bright folk out there who must have the ability to design one of these. Is it possible to build an autopilot with say, a heading hold, height hold, nav, loop, roll, 1, 1 1/4 and 1 1/2 turn spin, flick roll (you get the idea) functions? Program your aresti into the flight director perhaps? :)

[Fuji Abound]

.. .. .. but why would you want to do that?

[IO540]

Sure you could do that. The paperwork might be tricky.

[TheGorrilla]

.. .. .. but why would you want to do that?


Cos then I'll have my hands free to drink coffee.

[eharding]

.. .. .. but why would you want to do that?

You should see what happens when TheGorrilla tries to do it manually - that might answer your question. There's been a disturbing trend over the past year for the previously blameless Boeing drivers in our Yak group to become chief airbus fondlers - I'm half expecting to find one morning that they've moved the stick to the side console and fitted a picnic tray in the middle.

As to the practicalities, I don't see why not, given enough time, money and engine power. Doesn't the Typhoon have some automated manoeuvering systems which do pretty much what you want? (not sure about the flick roll though...)

[eharding]

Cos then I'll have my hands free to drink coffee.

It's a documented fact that the only thing you know how to do with coffee on a flight deck is to pour it into the electronics....

[TheGorrilla]

Hmmm... Ok. Tea then!

[Final 3 Greens]

The wing levellers on some 'mature' ships in the GA fleet can do some stuff like for no extra charge :}

[Fuji Abound]

Cos then I'll have my hands free to drink coffee.

Hmmm... Ok. Tea then!

In which case you need to fly you rolls correctly .. .. ..




YouTube - Bob Hoover (http://uk.youtube.com/watch?v=Xp2Uc9XvmjY)

[Duchess_Driver]

Tea, Coffee, Rolls........

Any chance of a biccy?

[IO540]

The KFC225 can do this stuff, off the shelf.

[eharding]

The KFC

That was as far as I got reading your post before I started getting emergency hunger pains, and an overwhelming desire for deep-fried factory-bred chicken and soggy fries. In a bucket. Damn you...damn you to Hell.

[BackPacker]

I was thinking of a whole bunch of funny replies, but I think a more serious answer would be deserved too.

First, there's the problem of inputs. A conventional AP uses the inputs that are found in the conventional sixpack: some mechanical gyros and the pitot-static system. Maybe a flux gate compass or something like that and some input from the GPS. In aerobatics, conventional mechanical gyros are out of the question in any case - you need something solid-state like for that, with unlimited freedom. Laser-based maybe? I'm not an expert in those. But that would tell you your attitude - important for all those ZLA figures. Oh, and the flux-gate compass would need to work properly in all attitudes, even 90 degree up or down, to do those 1/4 rolls in downlines properly.

Another input you'd need would be for a g-meter so that you can enter your loop with a fixed value, say 4G, and reduce the Gs over the top to 2Gs.

And the third additional input you'd probably need would be an Angle of Attack sensor, so you know exactly when to pull the stick all the way back to enter a spin or snap roll. (The alternative would be if the AP would know the exact aircraft mass, density altitude and such, to be able to calculate the exact moment of stall based on pitot-static data only.)

Of course, I'm assuming here that the AP has direct GPS input as well to know the exact location of the box, to calculate wind drift and so forth.

The second problem is one of output. You would need proper three-axis control by direct servo. Pitch, roll and yaw, with servos that can whip those controls from stop to stop instantaneously. None of these indirect controls where the AP slowly winds a trim wheel up or down. You'll want autothrottle too, especially if you have a fixed pitch prop.

And you'll definitely want to program the airframes limits into the AP. Not just the normal g limits, but also limits on rudder loads (snap rolls) and wing root bending. And maybe some limits on what the occupant (let's not call him pilot in this case) can sustain.

If you have all those, and have gotten it certified, I'm sure a clever person could write a program that would take your Aresti sequence, allows you to input a few tradeoffs in that sequence between altitude and speed, and then come up with an AP recipe.

Question is, would that be fun? I used to play chess but I gave up when I wrote a chess program during my computer science studies, and it beat me.

[Fuji Abound]

Anyway .. .. back to the more serious stuff.

Just as you thought IO540

The KFC225 has been a thoroughly unreliable product, failing a number of times in both pitch and roll. The roll failures have all been caused by the roll servo. The pitch failures have been caused by faults in the computer unit, or by the pitch servo.

I reckon it was not pulling the nose up enough before deflecting the ailerons.

oh, and why we were on the serious stuff, the little matter of an auto throttle might prove a problem, unless you are reckoning on maintaining full throttle over the top of the hammerhead. :)

and yes, Bob's other trick was to eat bickies at the same time as presumably keeping an eye on the tea on the glare panel, so you can have tea, bickies and no autopilot while still rolling, until you post it on Youtube and the b**st*rds want a meeting with you without the tea or bickies.

[eharding]

I was thinking of a whole bunch of funny replies, but I think a more serious answer would be deserved too.


If you knew TheGorrilla, you'd have put the effort into taking the proverbial out of him too - he deserves nothing less. However on a serious note...


Another input you'd need would be for a g-meter so that you can enter your loop with a fixed value, say 4G, and reduce the Gs over the top to 2Gs.


If you're pulling 2G at the top of a loop, you need help. 1G if your granny is on board, otherwise FLAB, taking the actual box wind into account.


And the third additional input you'd probably need would be an Angle of Attack sensor, so you know exactly when to pull the stick all the way back to enter a spin or snap roll.


You're trying to flick it, not kill it....just enough for 3G generally does the trick.


Of course, I'm assuming here that the AP has direct GPS input as well to know the exact location of the box, to calculate wind drift and so forth.


As it happens, we've been looking at GPS as a means of determining position during a sequence, but from a judging perspective - but using civilian kit on a reasonable budget, still doesn't seem to be a reliable mechanism when it comes to Advanced/Unlimited sequences.

I understand that negotiations are underway with a well-known military contractor to supply a ground-based tracking system as an automated line-judge at the upcoming World Aerobatic Championships which will be held at Silverstone this year - and on a more general note to the private flying community, please review NOTAMs for the area for August 18th-29th; you never know - the aforementioned ground-based tracking system may still have the military parts attached to deal with unwelcome box incursions.

[TheGorrilla]

if such a thing ever exists I would have fun swapping chips over with the elacs in my airbus!! :}

then, If i were a smart computer literate chap... I'd program in a perfect loop... Then stick in three neg flick rolls at the top!! :}:}:} Followed by a Cat3b mexican wave landing. (sorry Ed!)

Doesn't the Typhoon have some automated manoeuvering systems which do pretty much what you want? (not sure about the flick roll though...)

It does, apparently it's called the "sitting duck" button. I heard it's activated by pilot gloc or a little red tit that commands a recovery to straight and level... Genius move for a fighter!

Best consult the gurus on the military forum for a definitave answer. Ummm... Oh hang on....... They're either all in afghanistan or too old to know the answer :ok:.

[TheGorrilla]

Then again the day such an autopilot is approved will be the day this lot: YouTube - Men at work: Land down under!!!! (One of their best songs!!) (http://uk.youtube.com/watch?v=DNT7uZf7lew&NR=1)

Construct the ANO.

[will fly for food 06]

If you have the cirrus in heading and height mode then reduce the power. She can already do some crazy things:eek:. If you will want to try some crazy aeros have it in VS mode at 1000fpm and preselect FL100. More aeros for you:rolleyes:.

[BackPacker]

As it happens, we've been looking at GPS as a means of determining position during a sequence, but from a judging perspective - but using civilian kit on a reasonable budget, still doesn't seem to be a reliable mechanism when it comes to Advanced/Unlimited sequences.

Well, about half of those sequences are flown inverted so you would need a GPS antenna on the belly, and a GPS who can receive input from two (or more) antennae. Also the sample rate of one second may not be enough for the more snappy maneuvers. And your average GPS will not have gyros internally so determining the exact attitude of the aircraft for ZLA purposes would be impossible.

Combine this with the fact that you'll probably want a standalone (non-panel mounted), security-sealed unit, it'll probably be a long shot. Nice idea though.