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Circuit flying

Old 25th Jun 2017, 20:47
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Has anyone here actually experienced asymmetric flap deployment? I haven't seen it in 50 years of flying.
Well, sort of! The flap system had been disassembled, lubricated then reassembled. When the splined drive shaft was refitted, the guys managed to insert a shaft locking bolt through the 'female' socket without ensuring the 'male' shaft was fully inserted. All functional Passed. Coincidentally on the first trip afterwards we were flying a few simulated circuits at height. During one selection, the splined shaft fell out of the drive unit. Fortunately it was in a fairly advanced aircraft that sensed flap shaft rotation at both outboard flap screw jacks. When one stopped turning it froze the flap system before any significant assymetry occurred.

Oh, the maintenance instructions did include a warning to ensure the splined shafts were fully inserted prior to fitting the locating bolt!!!

Last edited by H Peacock; 25th Jun 2017 at 21:02.
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Old 25th Jun 2017, 21:20
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Originally Posted by MarcK View Post
Has anyone here actually experienced asymmetric flap deployment? I haven't seen it in 50 years of flying.
I have...twice.
Once in a Cessna 150 VFR and once in a Twin Comanche in night IMC.
Both in retraction though, one after a stall and the other going missed approach it rolled on us.
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Old 25th Jun 2017, 21:22
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Originally Posted by Collieflyer One View Post
Yes, not personally but I know that about ten years ago a student flying solo circuits at a nearby airfield in a C152 had the cable that lowers the flap on the opposite side to the flap motor break. He did a really good job of landing with 20 degrees on one flap and the other retracted.
Maybe.
What he should have done was land with flaps up or both at 20 depending how it failed.
Undo what you did last.
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Old 26th Jun 2017, 06:32
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I agree, he couldn't have landed with them both at 20 but he could have landed flapless. Twin comanches have a bit of a reputation for assymetric flap retraction if the nylon bushes are greased.
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Old 28th Jun 2017, 08:28
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I've flown with several ex-CFS instructors/examiners over the years for both FI and FIC work and recall asymmetric flap effect mentioned a number of times with the recommendation to avoid configuring flap in turns in light aircraft. 15 to 20 degree bank angle limits in climbing turns was also recommended to preserve climb performance, lookout and speed but again, in light aircraft and for teaching inexperienced trainees. Up to 30 deg level and descending turns however would be usual in the circuit if I recall.
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Old 28th Jun 2017, 14:33
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The 15 degrees angle of bank in a climbing turn goes back to the old days when for cross-country flights one always set course over the top of the aerodrome rather than just climbing on track.

In order to reach the set course height it was quicker to get there at 15 degrees angle of bank in terms of rate of climb than at (say) 45 degrees angle of bank where the rate of climb is significantly reduced. One problem of only using 15 degrees angle of bank in a climbing turn in to the circuit is that in high wing trainers like Cessna 172 the lowered wing blanks out the pilots view during the turn leading to possible traffic confliction.

Using 30 degrees angle of bank in the circuit makes stuff-all difference in rate of climb while the time in the blank spot is less.
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Old 29th Jun 2017, 12:22
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Originally Posted by Homsap View Post
BEagle...... Are you able to let us know why military circuits are a racetrack pattern, just wondered what the historical basis was?
I'd put it the other way around - why do civilians fly square circuits?

A circuit is surely intended to bundle a number of exercises (take off, climb, turn, level, speed changes, approach judgement and landing) in the vicinity of the airfield and as the engines of the early days were less than reliable one should never be out of gliding range of the field when in the circuit. That requirement, though often ignored today surely remains an important aspect of circuit flying.

The downwind leg ended with what is effectively a PFL - power off and adjusted with blips of engine (rotary). We now extend that a little to allow power assisted finals but the attitude judgement in that constant turn still replicates a PFL, good practice.

Square curcuits inevitably push the circuit too wide by the need to insert wings level sections on crosswind and base and you lose the safety of being in gliding range of the field and the all-important attitude judgement of adjusting your turn to achieve whatever gate is set for the finals point.

I can't see why civvies do these vast square circuits getting 6 - 8 circuits per hour instead of a dozen. Returning to racetrack circuits would solve the cross-country circuit syndrome at a stroke.
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Old 29th Jun 2017, 13:15
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At Sleap in the 1960's, the CFI was a pragmatist who appreciated that what ab initio students need is as many landings as can be squeezed into the hour, and that flying text-book circuits was a waste of time and money. Accordingly, he and the other FIs would take control at 200ft after take-off, fly the shortest possible route to line up on final at 500ft, hand over to the student to do the next touch-and-go, and take over over again at 200ft.

We were the only operator at the airfield, which made that easier. But most regional airports don't have all that many commercial (ie priority) movements during much of the day.

At Sleap in the '60s I flew as often as I could manage with the great Adam Wojda, an ex-RAF Polish FI with little respect for authority. One of my sessions with him was learning how to fly a really square circuit (not needed at Sleap, but elsewhere there were stuffy controllers, eg Sywell) by doing a neat little modified stall turn at each end of the downwind leg. He also taught me to sideslip the Auster from side to side down the final approach; it gave you a better view of where you intended to touch down. Evidently this was common practice in WWII tail-wheel fighters, known as fish-tailing.

Much later in life, I would make my feelings known that the flying club at an airport I worked at was simply defrauding its students by flying ridiculous "Bomber Command" circuits that took anything up to 15 minutes. Their problem was that the FIs didn't know any better. My heart sank every time I saw their Cessna 150s being dragged down a 2-mile approach with flap all the way and lots of power. This still goes on today, and it's wrong.
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Old 29th Jun 2017, 19:25
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All of my pre-solo circuits (Cessna 150) were power off abeam the numbers, first notch of flaps. Turn base (square corners), second notch of flaps. Turn final, full flaps. No additional power (but remember carb heat). Always made it to the runway.
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Old 30th Jun 2017, 02:26
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Ab inito training in the circuit is a lot more than learning how to flare and then touchdown. A proper square circuit reinforces all of the foundation skills of climbing, climbing turns, transition to cruise, level turns, descending turns and descending at a stable pre selected airspeed.

Before you can consist learn to land well you need to be proficient at all the other essential skills.

Good instructors will emphasize accurate co-ordinated flying at every part of the circuit, not just the last 10 feet.
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Old 30th Jun 2017, 07:59
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Originally Posted by MarcK View Post
Has anyone here actually experienced asymmetric flap deployment? I haven't seen it in 50 years of flying.
These poor guys did...
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Old 30th Jun 2017, 09:41
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The Heathrow Airspeed Ambassador crash was caused when left flap actuating rod failed allowing the already deployed flap to retract, so it wasn't technically during flap deployment. Several horses on-board were killed in addition to the crew.

Of the 2 BEA Tridents that were damaged, G-ARPI was tragically lost 4 years later at Staines due to a configuration stall. The droops (slats) were inadvertently retracted somewhat below the minimum retraction speed!
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Old 1st Jul 2017, 07:51
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Thank you for all your comments.

After a lifetime of flying many types, I think I will continue to do as before, using bank upto 30 degrees on the circuit, or less, but not more, to produce the radius of turn required dependant on x wind, circuit pattern, etc., It has served me well for 55 years.

Of course 15 degrees of bank is appropriate at times. On the VC10 it was a company requirement to roll off bank to 15 degrees before flap retraction and IIRC the bank angle on the Boeing 737 was only 15 degrees following engine failure requiring an emergency turn, optimising climb rate on one.

I was flying a Warrior which climbed perfectly well ( 2 up 2/3rds fuel, 22 deg, c. ) at 30 degrees of bank and I absolutely believe that any and all competent pilots should be able to easily manage flap operation in a turn., the risk of asymmetric flap being extremely remote. Perhaps I am wrong in believing that a light single will have enough roll authority to overcome asymmetric flap, just as the 757/767 could handle asymmetric leading edge extension.

Someone mentioned Bomber Command circuits, reckon I could have done a tighter visual circuit in a Canberra than some of the lumbering circuits I have seen on some single pistons !

I will discuss the issue with the CFI and try to get to the root of the issue.

Thank you , again, for your comments.
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Old 1st Jul 2017, 08:46
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I think it was suggested following the Dan Air Tenerife accident, had the aircraft made a wings level climb rather than a climbing turn, the aircraft would have cleared the terrain.

Also, yes some civilian circuits flown are unusually large, especially if you have an engine failure downwind or on base.

In answer to your originak question, 15 degrees in the climbing turn and all other turns 30 degrees. Flaps in the turn like sideslips in the turn should be exercised with caution, likewise sideslipping.

Should anyone be interested in the possible outcome of excesive bank angle and possibly sidesliping onto finals, the fatal accident of Chipmunk G-BDID serves as a warning.

Last edited by Homsap; 1st Jul 2017 at 09:03.
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Old 1st Jul 2017, 09:52
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Originally Posted by Big Pistons Forever View Post
A proper square circuit reinforces all of the foundation skills of ...
Does that differ from a proper racetrack circuit? Apart from having two more turns and the inevitable widening of the circuit which doesn't seem desireable under any circumstance?
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Old 1st Jul 2017, 22:03
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noflynomore.

The important part of my statement was the "properly flown circuit " bit.

What ever the circuit configuration if should be flown accurately. However the pretty much universal default circuit at civilian aerodromes is a square circuit.

What the air force used to do at military aerodromes is irrelevant.

With respect to "bomber circuits" the operative word is again "properly flown". If you are number 1 in your Cessna then the base leg should be turned so that the runway can be made with out power. If like me yesterday you were No 5 behind 2 Cessna's a Dash 8, and a 737 then your circuit should be managed to ensure proper spacing behind the jet with a flight path above the jet flight path and a planned touchdown beyond it's touchdown. This entailed a fairly wide circuit with circuit height maintained well into the final leg before a descent was initiated with a planned touchdown 1500 feet down the runway. My circuit ended up much wider than I would have flown if I was number 1, but was IMHO "properly flown"
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Old 2nd Jul 2017, 07:59
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Originally a circuit involved an aerodrome and an aeroplane. A properly flown circuit would be different for each aeroplane if you wish to maintain the runway on the wingtip whist downwind. With an increasing sensitivity to noise, aerodromes publish local circuit patterns as a single line on a map and then expect all pilots to follow the line. The line itself has been drawn on the basis of where the complainers live and hence places to avoid, nothing to do with where an aircraft actually goes if flying a circuit properly.

Too many instructors rush their students into the circuit, their comfort zone for teaching, and the poor student needs thinking time, so the circuit grows to accommodate this. Instead of going around if the aircraft in front extends, the next pilot extends further until the circuit leaves the ATZ!

As for 15 degrees of bank in a turn, often this emanates from the CFI and the poor instructor is just doing what he has been told. I recall one school where nobody was allowed to use full flap in case they have to go around!

Sadly, this nonsense gets worse rather than better
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Old 2nd Jul 2017, 08:18
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Whopity, agreed. Some ought to take a local area chart when circuit flying - they need to plan their downwind navex and rejoin!

I was once teaching circuits in RAF Bulldogs at a civilian airfield where we were flying two circuits for every one flown by some other SEP pilots. Some aircraft were flying downwind outside the ATZ. We certainly weren't going to follow them out that far so we flew inside their circuits. ATC were in full approval.
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Old 2nd Jul 2017, 09:12
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ShyTorque.. not sure if I was SATCO I would allow such a novel approach, but it can not be easy with civil and military traffic.

I remember once in the Maritime Alps requesting right hand circuits over an issue of terrain clearance in the left hand circuit on a particular runway, so ATC put me into a right circuit and everyone else in a left hand pattern.

It was only a matter of time before two aircraft ended up flying towards each other on opposite base legs, and an exchange of words. But the matter was resolved in the end.
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Old 2nd Jul 2017, 09:58
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Homsap, The other SEPs in question were flying upwind to the ATZ boundary, then crosswind to a lateral spacing of about 2.5 miles, flying the downwind leg completely outside of the ATZ then flying something like a 4 mile final. Our downwind spacing was as per RAF teaching, with the RAF roundel (about 2/3 wing span) just "touching" the runway.

Years later, in a civilian aircraft, our chief pilot received an irate phone call from an instructor who complained that he (in person) hadn't given way to him. It turned out that the CP was flying an instrument approach through the overhead (via the NDB) and talking to ATC. He briefly saw the other aircraft and assumed it was making an overhead join without calling. This was the aircraft flown by the instructor. Not only had the instructor left his own ATZ (he was flying circuits at another airfield, 6 nm away) on an extremely long "downwind" leg but he had entered the ATZ of another airfield to the overhead at circuit height, where the alleged incident occurred!

Last edited by ShyTorque; 2nd Jul 2017 at 23:27.
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