What is 'Gate Height' in a Loop..?

[scifi]

Hi All, I hope that some experienced aerobatic fliers could answer this question...
I have flown a few Loops in low powered aircraft, and Gliders, and realise that you can pull whatever G you like in both the first half of the Loop, and in the second half. I have always tried to limit this to about 3.5 - 4 G even though the aircraft was capable of a bit more.
So the question is... What determines the 'Gate Height'? Is it the height at which you would exit the Loop at the same height as you entered it, by pulling just moderate G. Or is it the minimum possible height that even by using maximum G you would still complete the Loop at the initial entry height..?
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[fantom]

Be very, very careful.

Loops are dangerous at low-level. If you pull hard at the start, you may never recover at the end.

[Capt Scribble]

The ‘gate’ parameters will be a height and speed at the top of the loop, with which the second half of the loop can be completed safely. Obviously, if you are fast at the top you will need more height to pull through, so the parmeters are not fixed.

[H Peacock]

What determines the 'Gate Height'? Is it the height at which you would exit the Loop at the same height as you entered it, by pulling just moderate G. Or is it the minimum possible height that even by using maximum G you would still complete the Loop at the initial entry height..?

The gate height could well be specific to a given display, ie if you want to come out of a loop say 500ft higher than entry then the gate height may well be raised accordingly. It certainly is not the minimum height to complete the loop at max g; it will have some allowance to ensure a safe outcome.

Speed can also be a significant factor for the gate. If you make the nominated gate height but are too fast you'll increase the diameter of the descending half resulting in an msd infringement or worse. Go through the same gate height too slow and you'll struggle to apply enough g-loading to 'turn' with possibly a similar outcome.

The F4 accident at Abingdon was an unfortunate example of not fully understanding the gate height v dynamics of displaying a high-performance aircraft.

[scifi]

Hi HP.. quote...if you want to come out of a loop say 500ft higher than entry... Well if you do that, you would not really be doing a good loop, and you would loose lots of points in a competition. However it might be a way to fudge the pattern by easing off and getting the two heights the same.
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[H Peacock]

Scifi. Agreed, but say your display started by going into a loop immediately after take-off, and was followed by a 4-pt roll. You'd obviously not want to do the latter at the same height that you entered the loop! I'm talking about display flying rather than competition aeros!

[BEagle]

scifi, you should have been taught all about 'gate heights' during your aerobatic training course.

[camelspyyder]

Sorry but with the OP's timing it sounds to me like a troll/journo question following the recent Shoreham announcement.

[Tankertrashnav]

Talking about journos, will they ever get over describing the manoeuvre as a "loop the loop" (most recently seen in yesterday's Times)? Also aerobatics are always described as "stunts". Do they use a report on one of Alan Cobham's airshows c1927 as a model for writing their pieces? :*

[melmothtw]

Talking about journos, will they ever get over describing the manoeuvre as a "loop the loop" (most recently seen in yesterday's Times)? Also aerobatics are always described as "stunts". Do they use a report on one of Alan Cobham's airshows c1927 as a model for writing their pieces? :*

They write for the public not the experts of PPRuNe, and those are the terms the public understand.

[just another jocky]

...and those are the terms the public understand.


Only because that's all they've ever heard them called by the media.


Same goes for "acrobatics". :ugh:


If the media could ever be accurate in their use of the language (yes, I know how ridiculous that sounds) then the public would be properly educated.

[POBJOY]

The slight limitation with a DA clearance is there is no actual requirement to 'practice' at a specific location, or show how you would adjust for increase in AC weight or even more the temp above ISA for the area location at the time.
In the case of the T7 Hunter this had a reduced performance compared with its single seat variant in service at the same time, therefore making it even more important to demonstrate the knowledge of this situation to an examiner.
Regulations at airshows are usually directed to protect both 'performers' and spectators alike, with the ANO still in force to cover those outside of the immediate display area. It is quite evident that some locations will never be suitable for high energy aircraft to be able to comply with 'modern' regulations, and that organisers of such shows will also have to consider a duty of care on a much wider basis than before. At the end of the day the pilots 'decisions' on the day are far more important than a extra mountain of paperwork and boxes to tick, and I think this should form part of the DA process.

[Sloppy Link]

Steady on Tiger, you are encouraging others to engage in a conversation that will feed the troll beasts. Beware.

[scifi]

Hi Beagle, well no, I was never told anything about gate heights, that is why I asked the question. I own a semi aerobatic glider that is cleared for several different easy manoeuvres, but nowhere in the owners manual does it give any figures of how much airspace is needed for each. So if the manufacturers don't give us a figure for this gate height, then it must be something the pilot has to calculate. If he finds this estimate at say 10,000ft, then the result won't be accurate at sea level.

The only figures given by a manufacturer, that I know of, related to the safe altitude to be used for stall/spins, and this limitation was only imposed 30 years after that plane had been in service, and following a series of spin accidents.
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[rjtjrt]

scifi, you should have been taught all about 'gate heights' during your aerobatic training course.

I fail to see how this post above from BEagle is in any way helpful.

[Flap62]

I’m sure he will answer for himself but, at a guess, I suppose he’s suggesting that the OP should be familiar with the term from his/her aerobatic course and if they haven’t done the course then it’s a moot point as they shouldn’t be flying aerobatics.

[BEagle]

Flap62, correct. The only advice to be given to someone flying 'self taught' aerobatics is to do a proper course.

Anyway, from 8th Apr 2018 civilian pilots will need to hold a Part-FCL Aerobatic Rating if they wish to conduct aerobatics in EASA aircraft.

[The Old Fat One]

I fail to see how this post above from BEagle is in any way helpful.

Well what Beags said is exactly what went through my mind and I'm not even a pilot...

I own a semi aerobatic glider that is cleared for several different easy manoeuvres, but nowhere in the owners manual does it give any figures of how much airspace is needed for each.


...and now I've read the above, i'm thinking a whole ton of us will be on the same page.

But I don't think Op is trolling about Shoreham though....just a coincidence I expect.

[H Peacock]

I recall an RAF Tucano display practice accident where (astonishingly) the driver showed little if any awareness of gate heights!

[LOMCEVAK]

In low speed aerobatic aircraft a 'gate height' is not applicable because the pitch rate at the apex is high and by the time the pilot has assimilated the height and made a decision the aircraft is in a significant nose low attitude and rolling to wings level erect and pulling back to level flight may actually lose more height than continuing to pull through, especially if the roll performance is poor as in a glider. Therefore, in such aircraft the key parameters are a minimum entry speed and a minimum entry height such that if the upward half is flown correctly (and there will be little scope for variation) then adequate height will exist at the apex for a safe second half.

HP, as I recall the accident to which you refer was a stall turn during which the pilot was simulating a minimum cloudbase, was fast at entry so reduced power (to idle?) and selected the airbrake out. He was, unsurprisingly, too low at the apex to complete the manoeuvre. Therefore, this was not a 'gate height' related accident.

[scifi]

Thanks Beagle for the 8 April 2018 date, looks like I will have to abandon any more attempts at improving my Lazy Eights...


Aerobatic flying training | British Aerobatic Academy (http://www.britishaerobaticacademy.com/easa-aerobatic-rating)
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[Shaft109]

Hello Scifi - I've completed that course with Adrian in the Extra (fantastic aircraft BTW).

You'll learn all the basics required in theory and practice but the caveat is obviously each type is different and energy management / roll rate / performance etc can't be transferred across directly so planning and preparation is required - but sure the BGA can direct you to a Aerobatic gliding instructor after you've completed to hone that aspect.

i.e. the Extra can roll 360* per second but all gliders I've flown are in the order of 60*p/s or less.

I chose to fly at Conington because I specifically wanted an aircraft built for the job with very few limits in that regard - I won't be trying to roll a PA28 any time soon.

And you'll have a smile you can post a wok in afterwards too.

[dook]

....you should have been taught all about 'gate heights' during your aerobatic training course.

Beagle is correct.

For my competition work I was fortunate enough to have a "manager" who was an ex-member of the Gemini team.

In order to win in a professional completion with a 500ft base height, all manoeuvres, horizontal and vertical, had to be at this height.

Therefore looping manoeuvres had to be started and completed at this height. The gate height is a speed/height combination in order to complete it correctly.

For the OP it means a combination which ensures safety. The common mistake is pulling too hard on entry to a loop. If the top gate is not made then the escape manoeuvre is a half cuban eight. Escape manoeuvres are vital.

I did win an international competition btw, and judged one.