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Downwind leg - how wide from the runway?

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Downwind leg - how wide from the runway?

Old 4th Jul 2019, 12:20
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Downwind leg - how wide from the runway?

Over the years, Melbourne based PPRuNe contributors occasionally complain about the wide circuits flown at Moorabbin. It probably happens at other capital city general aviation airports in Australia as well. . As one instructor rationalized, "Wide circuits give time for student pilots to settle down." That is not a credible reason. On the contrary, wide circuits can be frustrating, annoying (and costly) to other pilots who fly intelligent circuits commensurate with aircraft type.

Some Boeing manuals (Boeing 737 for example) recommend a standardized two mile wide downwind leg for their types. It follows that a half mile width should be the norm for typical flying school trainers. The circuit width should not be tailored to the pilot but to the type of aircraft and the pilot should be trained to that standard - instructors please note.
The following article discusses circuit training:
https://pilotworkshop.com/tips/traffic-pattern-track/?utm_source=totw&utm_medium=email&utm_term=7-3-2019&utm_campaign=tip
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Old 4th Jul 2019, 12:52
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Depending how well I correct for wind on the day, 850-1000m in the RV-9...And you can get a touch-and-go circuit in every 3 minutes 20 seconds if there's no one else about to conflict with!

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Old 4th Jul 2019, 12:52
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Ideally, it depends on the glide ratio and airspeed of the airplane in question, to be able to make the runway in the event of engine failure.

Realistically, it depends on other practicalities, such as skill level of the pilot (particularly in the early learning stages).
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Old 4th Jul 2019, 13:12
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it also depends on the climb rate as instructors won’t let the downwind turn start until 1000ft on crosswind. My guesstimate for the width is about 800 - 900m for a C172 from my time there.
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Old 4th Jul 2019, 14:14
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I was taught during basic military flying training that at an unfamiliar airfield, when unsure of the downwind spacing, put the edge of the (inboard) wingtip just on the runway. Certainly worked as a decent approximation for smallish aircraft
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Old 4th Jul 2019, 14:24
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In RAF SEP, low wing aircraft we used to teach students to put the roundel on the outer wing over the runway in use. The idea was that it kept you close enough so in the unlikely event of the engine failing, you would have a chance of making the airfield, if necessary. We also flew "oval" circuits, not the much larger, "civvie" rectangular ones. Anyone going outside of the normal pattern, such as when committing the heinous crime of extending too far downwind might be directed by the duty instructor to go around onto the deadside and rejoin the circuit.

These days it's all too common to see aircraft supposedly in the circuit of minor airfields leaving the protection of the ATZ on the downwind leg - obviously many of these pilots aren't looking outwards, only in towards the field; not at all sensible.
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Old 4th Jul 2019, 14:26
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it depends on other practicalities, such as skill level of the pilot (particularly in the early learning stages).
Maybe - Maybe not. Assuming the instructor has the ability to first demonstrate to the student the correct width of the downwind leg along with required turning points, then the student has something to aim for. But if the instructor lets the student fly the circuit he feels comfortable with, then that is poor instruction because that could impact other users of the circuit. A learner driver would probably be happier driving down the middle of the road rather than keeping to the left. But most driving instructors wouldn't allow that to happen.
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Old 4th Jul 2019, 23:15
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Varies for every aircraft as there are lots of factors like how steep the descent is, speed, likelyhod of an engine failure, flaps, can they sideslip. In anything slightly higher performance, if you conduct a turn at 120kts the diameter would be roughly 1-1.2nm (1800-2200m). So a minimum of that is needed.
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Old 5th Jul 2019, 03:22
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Originally Posted by Sunfish View Post
it also depends on the climb rate as instructors won’t let the downwind turn start until 1000ft on crosswind. My guesstimate for the width is about 800 - 900m for a C172 from my time there.
Not true where I learnt my circuits. We were taught early to continue the climb in the turn to downwind and more often than not you find yourself patting your head and rubbing your stomach stopping the climb while finishing the turn. Don't tar all schools with the same brush.

Originally Posted by sheppey View Post
Maybe - Maybe not. Assuming the instructor has the ability to first demonstrate to the student the correct width of the downwind leg along with required turning points, then the student has something to aim for. But if the instructor lets the student fly the circuit he feels comfortable with, then that is poor instruction because that could impact other users of the circuit. A learner driver would probably be happier driving down the middle of the road rather than keeping to the left. But most driving instructors wouldn't allow that to happen.
The majority of our circuit is over water so instruction was more aligned to the 45 degree angle back to the runway over you left or right shoulder. First turn at 500ft, turn to downwind 45 to the field, similar for turn to base. Seems to work out reasonably well. So even without turning points on the ground the instructors should be able to offer some form of guidance.
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Old 5th Jul 2019, 06:01
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In my previous life at Parafield airport we had the same issue as Moorabbin, constantly wider and wider circuits - particuarly when there is a tailwind on crosswind or downwind.

In a single engine aircraft - close enough to glide from a downwind position and comfortably glide in (0.75-1nm). Larger aircraft operate higher and faster, so flying the same sized circuit would not be practical. The aircraft I operate now (medium turboprop) we aim for approx 1.5-1.8nm spacing with a 1500' circuit.
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Old 5th Jul 2019, 06:18
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The instructor should demonstrate correctly then the student follow. The first turn onto crosswind is done at 500' AGL but the turn onto downwind is to set up the downwind leg at the correct distance from the runway, not an altitude. We often get "mega circuits" here at Jandakot and instructors just letting them wander to the edge of the control zone. It's very annoying when you have to follow an aircraft that is taking the scenic route.
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Old 5th Jul 2019, 08:06
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I never said it was correct, just what a certain school did. Climbing turns, descending turns, spirals to loose height were not part of their syllabus. The CFI also hated side slipping.

The lax behaviour at YMMB soon boiled down for the ab initial student to : “aim for this factory, then turn to follow xxx road, then yyyy road, aim for vegetable gardens, then golf clubhouse, etc., etc.” Nothing useful was taught about visual cues apart from “put the strut on the runway, about 45 degrees’ to the point that I still have trouble judging turning points on short narrow strips and that has cost me $$ in go around and overlong final approaches to compensate.

Last edited by Sunfish; 5th Jul 2019 at 08:23.
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Old 5th Jul 2019, 08:47
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Originally Posted by Clare Prop View Post
The first turn onto crosswind is done at 500' AGL
Is it not 700ft these days?
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Old 5th Jul 2019, 09:09
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Originally Posted by Stickshift3000 View Post
Ideally, it depends on the glide ratio and airspeed of the airplane in question, to be able to make the runway in the event of engine failure.

Realistically, it depends on other practicalities, such as skill level of the pilot (particularly in the early learning stages).
That is a good summary --- unfortunately large circuits are very good for the flying school's bottom line --- one then justly (in)famous school in the Sydney area could only manage four circuits an hour --- and that was only part of the student rip-off. ---- and the sodding "CFI" used to complain, at the drop of a hat, that other aircraft cut inside him --- when he was so wide he was well out of the associated control zone, let alone a reasonable (as per Stickshift 3000) distance for something doing 75Kts.

Keep it tight ---- you might be surprised how small a circuit can be, in a large aircraft,

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Old 5th Jul 2019, 09:18
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Originally Posted by Squawk7700 View Post
Is it not 700ft these days?
https://vfrg.casa.gov.au/operations/...it-procedures/
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Old 5th Jul 2019, 11:17
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Originally Posted by Squawk7700 View Post


Is it not 700ft these days?
VFRG states “not less than 500’ “ for turn onto crosswind.
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Old 5th Jul 2019, 11:59
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This remark from a former RAF Canberra pilot who was sent to Canada for his flying training. Of course not all Harvards were in the circuit at the same time but you can bet circuit discipline was tight.

"I remember training in Canada on the Harvard at RCAF Penhold Alberta (near Red Deer) in 1957.It was quite normal to have 60 or 70 Harvards serviceable on the line in the morning.(100 deg F in Summer -40 in winter) Cheers"
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Old 5th Jul 2019, 12:56
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Originally Posted by sheppey View Post
Of course not all Harvards were in the circuit at the same time but you can bet circuit discipline was tight
Having 7+ light GA planes in the circuit is demanding (non-towered), but fairly common where I fly. Not usually a problem when there's good discipline and speed control, but this does vary with trainees.


Last edited by Stickshift3000; 5th Jul 2019 at 23:33. Reason: Context
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Old 5th Jul 2019, 15:32
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Originally Posted by KRviator View Post
Depending how well I correct for wind on the day, 850-1000m in the RV-9...And you can get a touch-and-go circuit in every 3 minutes 20 seconds if there's no one else about to conflict with!
Whaat!? You lucky bu99er. I am lucky to get 3 touch and go's in a 1 hour lesson which has made my training at a very busy airport slow and expensive.
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Old 6th Jul 2019, 00:58
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Originally Posted by Stickshift3000 View Post


Having 7+ light GA planes in the circuit is demanding (non-towered), but fairly common where I fly. Not usually a problem when there's good discipline and speed control, but this does vary with trainees.

Folks,
"Back in the day", with 05/23 in full swing at (then) ASBK, 12 in the circuit was common, with 3 of 4 more or less abreast on final for the grass and runway.
Most of us were "logging" 100h per month.
Sadly, these days, 3 or 4 per hour would be more like it.
Tootle pip!!
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