What Does High Key mean when in the circuit?
 

Morning All

I have often heard the term High Key when an aircraft is in the Circuit. What does this mean.

Cheers

Glider 90

High key
 

I realise the use of it may vary slightly from type to type but generally it is a term used when doing a PFL pattern. It is roughly equivalent to the downwind call (low key or final key may be used for the finals call). The orientation may differ between aircraft but it is designed to allow a constant glide angle to be maintained from overhead the runway until touchdown.

I’m sure others can provide more detail for specific aircraft types. I can only speak for the Hawk. Our High Key (for a circling PFL) is 90 degrees off at the upwind threshold.

BV

RAAF Mirage IIIs called High Key entering the downwind leg at 14,000 ft ... quite stimulating to watch from the Tower, and I suspect even more so in the cockpit.

Going back a few decades: for the Hunter we used 5-6000 ft agl as High Key, entering the downwind leg, 210 kt clean. Low Key, abeam touchdown, ideally 3000 ft.

Heights
 

I should have added that HK is approx 4500’ and LK approx 2500’.

Always think wind of course!

BV

Wot's a PFL ? :E

LFH (Glider 1961)

..........

Practice Forced Landing:ugh:

Different from an AFL, as gliders do that all the time.

Recall having a ride in a Belgian 104 (which wasn't for the faint-hearted) and being told their High Key was 22,000ft!:oh:

There is a long thread on this on a certain other place that concerns flying little planes with a mix of outrage from some GA pilots and enlightenment from others, that people should use such terms when flying in 'GA' and not 'Military' airspace. For some people, being an ex-mil pilot winds them up no end before you've even got past the 'hello how are you' stage... Maybe previous offerings of pomposity have wound them up or maybe its just resentment at not having made it into the RAF. Either way, an awareness of different ways of skinning a cat and that others may not understand the words you use may be the way forward...

Or just join for a break to land every time... :8

Just listened to Arnulf Hartl being interviewed about flying the F104 and there is an interesting bit about partial power/dead stick approaches!! For those who haven't listened, these are an excellent series of podcasts - normal blokes talking about the planes they have flown.

Someone will correct me with the precise details but ISTR that in the mighty Bullfrog, High Key was about 800', with Low Key about 400-500' depending on the CSLA and how that was going ....

I'm sure it wound up the civvies no end (and probably rightly so) when we practised diversions into a nearby civilian airfield. You could almost hear the amusement in the controllers voice there as he interupted whatever they were doing and said to his assembled throng ..

"All stations, clear the circuit immediately, military aircraft inbound" and their 'pi$$ed-offness' when a Bulldog trundled into sight, did an approach, not even a TnGo, and then bogged off again..

JP Mk3a and Mk5 Hkey @2500' agl, Lkey @ 1500' agl.
Lkey downwind abeam RW threshold.

Remember early Microsoft Flight Simulator?
It had red boxes in the sky, you flew through them to achieve the result required ie approach to land.

High Key, Low Key etc are "Key" points (or "Gates").
Achieve each gate in sequence and you should achieve your objective ie PFL.
If you are not at the required height, speed and position, you may be able to continue your (now modified) pattern or have to abandon it - with all that implies.

It formalises a procedure and makes it more likely that you will be successful in your task, be it practice or real - it gives you an early warning too if things are not going "to plan".

lsh

:E

Cargosales wrote: For the Bulldog PFL, ideally you would approach the desired landing area at 80KIAS and 2-3000' agl before tracking to 'Point 1' or High Key when the initial aiming point 1/3 way into the field appeared immediately in front of the wing leading edge. Then decelerate to 75KIAS and keep gliding straight ahead until the touchdown point appeared just behind the trailing edge (Point 2). Then turn with 30° AoB to track crosswind, aiming at a selected feature and allowing for drift, until the touchdown point appeared immediately ahead of the tailplane (Point 3). That was 'Low Key', at around 1500' agl, when you started a continuous gliding turn at 20°AoB at 75KIAS with Inter flap aiming to run the touchdown point along an imaginary line from its location on the left side of the aircraft to directly in front of the windscreen. If you were getting below the line, you increased bank and held the picture until you regained the imaginary line, then ease off the bank and reassess. Once straight in to the field, provided you were certain of getting in and were not below 200' agl, you would lower full flap and use a touchdown aiming point closer to the downwind end of the landing area. We used to practise this down to 100' agl when dual or 250' agl for student solos.

cargosales,


"All stations, clear the circuit immediately, military aircraft inbound"

In what world was that ever heard?

I think one of my gliding instructors had flown WGAF F-104s at some point in his career.

This one. At a civvy airfield in the West Mids that we were approaching to be precise.. I remember it clearly because it was so dramatic and pointlessly OTT..

Thanks BEags .. that sounds more like it. Guess I was thinking of normal circuit height, not PFLs.

Cheers, CS

I still have, tucked away in a filing cabinet, the NOTAM with the Space Shuttle emergency landing profile into Fairford with, along with the flight path/timing circle details such pearls of information that it would be an unpowered approach......

maybe they had a lower opinion of the military than you did....................

:):)

I believe we have a winner!!!!

Not always. Only when all the lift has disappeared.

Those dratted Lift Pixies are SO unreliable

Great reply, ORAC. And I thot the initial question was a really great one, and I don't know what the sailplane/glider folks call there position in the pattern ( we yanks call it pattern versus circuit)

The shuttle circle was really well thot out and allowed various approach headings and even altitudes.

Having practiced the precautionary flameout or engine problem patterns many times back in my early days, the terms "high key" and "low key" ring a special bell. And then comes the day you have to do it for real, heh heh. And I did.

Was shot up and leaking fuel like crazy, so deadsticked my A-37 into the big airport at Saigon. The jet was brand new and we did not even have a procedure in the books yet, so I added speeds from the T-37 trainer model procedure and recalled my numerous practice "circuits' from my T-33 experience. Was able to get the critter onto the rwy and only had blown main gear damage and all those holes in the fuel lines. So the jet flew again a few weeks later.

USAF prohibited flameout approaches a few years later, and the F-16 was the first one that was allowed to practice and actually do some when the motor failed within few minutes of a suitable field. High key was like 8,000 ft above the field and low key maybe 3500 feet or so. We played the altitude more than distance from the rwy, but that kite had a really great glide ratio ubntil you lowered the gear. We had one troop do a straight in deadstick over at Wendover, UT. Whew!

Gums sends...

TNX, Megan. Nice video and newer HUD display than I had.

I was instructor for the Wendover guy and possibly the one at Tampa/St Pete.

The pure hydrazine EPU only lasted 6 or 7 minutes, but you could help by being smooth and easing the hydraulic demand. Another thing was using the jet fuel starter if you had gas left but the big motor was tits up. That allowed some hydraulic pressure that the EPU didn't have to provide.

neat thead....

Hello All

Thanks for all the replys, Have learnt a lot about the High Key term.

Cheers
Glider 90

High key, low key, base, finals... But there is a diagonal as well to keep the landing area in sight all the way round the circuit, and every circuit is a one-off due to the need to arrive in the right place (or a suitable place) on the airfield. Finding oneself in 6 knots of sink can be 'interesting'.

What is currently being taught at the Elementary level is a direct derivative of this. :ok:


High Key is now 2500-3500ft agl and Low Key is now abeam the Initial Aiming Point, around 1500ft but can be above or below. The imaginary line is called the Sight Line Angle.


A field approach is far easier because if you find yourself high or low, you have many choices to correct it: change the landing direction, change the field, S-Turn to lose height or even sideslip (used by myself last week on a Precautionary Forced Landing). To a runway, there's less choice but varying the angle of bank varies the touchdown point so it can be quite easily controlled.


We try to teach our students to use plain language when doing "something military" at civilian airfields, so High Key would be "Deadside, 3000ft, right-hand glide approach to runway XX" but often we have to ditch the military stuff and fly square and very wide circuits. Shame though, cos even in a Tutor, a VRIAB is good fun! :}

I well remember an old and hairy ground instructor's reaction to "High key" Low key", having had several engine failures himself on singles , including with the J.P.
His method, from medium altitude, was to head for the overhead of the nearest R.A.F. Airfield ,broadcasting his intentions and getting the circuit cleared. Then spiral down until by aspect it was comfortable to get on to one of the runways and then deadstick well in.
He admitted having a dilemma on one occasion as whether to go for Cranwell or Barkston. He chose the latter:
"Since that was where I'd left my bike"

Of course finding an RAF Airfield now is a bit more difficult..........

Watched/listened to the shuttle return to Canaveral in the 80s with them calling heights and speeds over the radio, it's one hell of a glide approach as they were over the Gulf of Mexico still at Mach 25! Bizarrely, you hear a double sonic boom as they come back through the sound barrier.

Used to do a glide approach into Muharraq in the VC10 many years ago. IIRC 30000 feet, 30 nms DME, select idle power, use combination of speed brakes, gear and flaps/slats to adjust glide path, low key at about 2500 feet abeam touch down IAP, turn final and select full flap - or not.

Did them too in the Ten, but of course those figures, for whatever aircraft, is invariably for a PFL (ie practice). So the engine was at idle. Try that will an engine seized, especially if one cannot feather the prop, and one comes down rather quicker. However, rate of descent does not matter if one flies the 'constant aspect technique'. I works for me in a Bulldog and it worked for me in the VC10.

Ah sharpend, a "madeleine moment" that instantly dragged out of memory the JP PFL mantra:

"Lowering half flap to simulate the drag of a dead engine".

Always wondered how accurate that was; certainly "forgetting" it for a bit made a useful increase in range............

That's essentially the same as the more formally laid down RAF procedure, but without the key point numbers.

The advantage of the Bulldog is that the prop goes to coarse pitch, all by itself.

And the astronauts used to practise this shuttle approach using a heavily modified Gulfstream II, each shuttle pilot doing approx 700 approaches in the aircraft.

The cockpit was redesigned to be the same as the shuttle, it was flown using the same HGS/HUD. If I remember correctly the technique was to start around 37000ft over the airport, main gear down, flaps into a neg position, thrust reversers deployed and reverse thrust applied, the descent profile was almost identical to the shuttle arriving on finals following the shuttle PAPI system to about 5000ft for a go-around.

The idea was to get the descent profile correct not the actual landing, I seem to remember there was a magazine article published describing the flight profile somewhere in the eighties.

https://upload.wikimedia.org/wikiped...g_Aircraft.jpg

https://upload.wikimedia.org/wikiped...or_cockpit.jpg

Maybe this will be helpful:

https://i1.wp.com/www.avgeekery.com/...key1.jpg?ssl=1
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