Circuits - Oval or square?

[shags_j]

Hey all,

 

I've done quite a few hours in cessna's before moving over to RA Aircraft. First I flew in teh QAIRTC (Air cadets) a while ago then moved on to another flying school at archerfield.

 

At both of these I flew oval circuits. I found them quite easy to master in all the 5 types of aircraft I flew there and provided beautiful spacing and quite easy to master circuits.

 

Now I am at a school that insists on square circuits. I was just wondering why one or the other? Is there any advantage? Is it an LSA thing?

 

Second in flying square circuits how far should you make the crosswind leg?

 

Amazing that I feel really comfortable flying then all of a sudden something so small like this and I have all manner of questions floating around.

 

Cheers,

 

Shags

 

 

[gofastclint]

At The Oaks its square. I always thought that RA was square. I know the "old boys" get very annoyed if a GA guys starts flying oval circuits.

 

 

[shags_j]

Yeah i noticed that...

 

 

[Guest ozzie]

rectangle actually

 

 

[Matt]

Hi Shags,

 

The air cadets would fly "like the military" who fly oval circuits for many reasons...most related to fast landing aircraft with poor forward visibility at high angle of attack / slow speed.

 

I personally fly oval circuits wherever possible. Couple of reasons, firstly the flying manual for the CT4 only talks about oval circuit operations - being a military aircraft. I also find the approach easier, a constant radius descending turn avoiding tight turns at slow speed, the threshold is always in sight etc.

 

Regarding crosswind leg / downwind leg spacing - I was taught to be no further than 1nm from the airfield whilst in the circuit to allow for a glide approach in the event of an engine failure in the circuit. For each aircraft I fly, I learn to identify reference points where the runway intersects at circuit height i.e. downwind spacing in the CT4 has the runway centreline track through the roundel on the wing. base turn is commenced when the runway threshold is 1 chord length behind the wingtip (not 45 degrees) and 20 degree angle of bank with a 500fpm descent rate etc. etc. again, all of this is in my flight manual.

 

There's nothing to say you have to fly rectangle circuits or that the crosswind or base legs have to be straight...that I'm aware of.

 

 

[shags_j]

Cheers. That all makes sense. One instructor I had was telling me to extend cross wind to this particular landmark then turn. I didn't like that as it didn't really show how to do it anywhere other than that runway.

 

So how would you measure 1nm in the air? Do you get used to that kind of distance guessing?

 

 

[philipnz]

Rectangular. I've got used to selecting 15 degree flaps on downwind 40 on base. I prefer not to move flaps while i'm turning so that makes me keep straight.

 

Plus where I fly it's really busy and it's so much easier to keep an eye on aircraft if they are flying straight lines.

 

 

[Tomo]

I'm getting taught to go to about 45 degrees off the end of the runway, doing that at circuit height...(1000ft)

 

and rectangular circuit it is.

 

 

[Guest Crezzi]

There's nothing to say you have to fly rectangle circuits or that the crosswind or base legs have to be straight...that I'm aware of.

Granted its not the same as a mandatory requirement but the diagrams in the Visual Flying guide all illustrate rectangular circuits. I think they would be considered the norm for civi operations though there are exceptions.

 

Cheers

 

John

 

 

[Yenn]

Rectangular has been the norm all the time I have been flying, except for the military.

 

 

[lazerin]

Rectangular at normal circuit height i.e. 1000ft.

 

Oval (amended - racecourse) when doing low level 500ft circuits or precautionary search and landings.

 

EDIT: Ozzie's post below is a more accurate description of what i meant.

 

 

[Guest ozzie]

The racecourse circuit is another. must freak the ponies out

 

 

[Guest Maj Millard]

Yes I generally fly a rectange type approach also, but also can be found flying a circular curved final approach off of downwind, depending on traffic numbers of course.

 

Years ago in California I was flying around in my scratch-built WW1 replica Albatros C1, complete with German' Balkankrutzes' on the wings. (German crosses to you and I) I was invited through the grapevine, to come on over to this very tradition type old fashion small airfield, where many old replica and antique type aircraft lived.

 

Prerparing to do so i was advised that I had to approach and land, at the field using a certain style, well practised in the 20s and 30s aviation era. This was the only accepted pattern style accepted at this private airfield.

 

Radio usage was definitly out, and would be frowned upon if used at all.

 

The approach had to be made above the field, at around 1500 to 2000 ft, followed by a continuous 'circling' descent above the field until lining up and landing on the appropriate runway. It was a see and be seen situation, and common courtesy was to be exercised.

 

After performing this style of approach and landing im my little German crate (with no radio calls) I found it to be very natural in a way, with excellant visability all the way, due to the continous circling approach. Probably a lot less traffic back in the 20s and 30s.....shame in a way really.

 

 

[Deskpilot]

The racecourse circuit is another. must freak the ponies out

What's the old saying, "Horses for courses"

 

Rectangular might be the norm, but engine failures in cct (on cross/downwind) usually require 'racecourse'. so practice both.

 

 

[poteroo]

The accepted procedure for all circuits is rectangular, ie, allowing for wind so that the track is rectangular. Parallelograms are NR !

 

For 500 ft circuits, as far as I'm aware, it's still a rectangular track for civilian aircraft.

 

However, for bad weather/limited visibility circuits, or arrivals in bad wx, or where a precautionary is intended, the best procedure is an oval circuit. The turn from downwind to final is made from just passing the threshold, and is best started with half flap extended. Full flap comes in turning final, (which is at the apex of the 180o turn), and you roll out at about 100-150ft agl.

 

The descending turn onto final allows you to see your threshold all the way down - and can save your bacon in wx where visibility is changing frequently.

 

It may be difficult to pracrise these at a CTAF® or other busy airport. I believe this sort of stuff should really be part & parcel of the cross-country training syllabus. To do this, and other close-to-ground procedures - all instructors should be low level rated...as part of their training package. A bit radical, I know, but unless the bar is raised for instructors - we're going sideways.

 

happy days,

 

 

[shags_j]

Well I was using oval circuits at archerfield which on some days is an extremely busy airport. I never had a problem doing them there.

 

I just thought it strange after learning one then all of sudden having this whole new world open up.

 

 

[Bidgee]

I was taught rectangular cts. firstly it gives you a good idea where all the other traffic is. You should be able to hear a radio call, look out the window and spot them. Not sure if this possible with oval cts.

 

Secondly good landings are all about consistency and preparation. Both of these are easier on rectangle cts (for less experienced pilots anyway) eg the hold off required to parallel to the rwy on downwind gives you a good estimate of any xwind so you know the strength when you turn base and dont overcook the turn onto final.

 

Second in flying square circuits how far should you make the crosswind leg?

Extend xwind so when you turn DW you are within gliding dist of the rwy. I trained in a low wing so looking out the port window I kept the rwy just inside the left wing tip. You are better off using a reference with the a/c & runway rather than landmarks for judging turns. A good reference in the a/c I trained in was to turn base when the end of the rwy was 45 deg off the wing.

 

One thing I found that threw my judgement was landing at aerodromes with different width runways than the one you normally operate it. The different width makes you seem either closer or further away than you actually are.

 

Scott

 

 

[shags_j]

Thanks for that Scott. That was really helpful.

 

I guess which is harder really depends on what you were taught first. I find oval soooo much easier. Really though it's neither here nor there.

 

 

[Guest ozzie]

yep narrow ones look longer and wide ones look narrowerit can catch you out if haven't read your ersa

 

 

[Guest Cloudsuck]

G'day Shags,

 

I agree with Matt above. I was taught rectangle circuits when I was taught to fly in a Drifter and it is the most common circuit, however, when I was doing my PPL, I was taught by a guy who had heaps of Pitts time and he made me fly oval circuits.

 

I think they are great and a must for any plane in which you loose sight of the runway over the nose on final. I always did oval circuits in the Yak for that reason and they feel so nice. If you ever watch really good aerobatic and warbird pilots they do oval circuits most of the time.

 

I reckon that you are less likely to stall spin in an oval circuit as you can constantly make minor variations in the turn to roll out right on final instead of overshooting on 'base to final' and then trying to tighten the turn with bottom rudder and hold of bank :black_eye:.

 

In any case, I would do what your instructor wants and when you get your pilot certificate, fly the oval circuit if you want.

 

If you ever want to see a really nice oval circuit, get the video of 'One Six Left' there is a really nice clip of Pitts doing one circuit viewed from the cockpit looking back at the pilot. Just beautiful to watch.

 

P.S. I have done lots of circuits at Archerfield and have used either type. The most common there is rectangle (as with everywhere else). Depends on your instructor.

 

 

[Yenn]

Maybe an oval circuit is the way to go with a plane where you lose sight of the runway, but there are not many like that. I fly a taildragger and I only lose sight when I flare.

 

To use oval circuits when everyone else is using square is a pain in the butt. I was called up by a supermarine spitfire at Bundy last year at the air show, he asked my intentions and I was on base, following a Cessna. He then overtook me and cut inside to land before me. I never did find who was piloting it as all the people on their stand disclaimed all knowledge. My slowing down to give clearance from the Cessna was all negated and I had to land long after the spitfire had turned off. I don't know what happened to the dozen or so aircraft following me. Spitfire nice plane, pilot poor quality.

 

 

[Guest Cloudsuck]

Maybe an oval circuit is the way to go with a plane where you lose sight of the runway, but there are not many like that. I fly a taildragger and I only lose sight when I flare.To use oval circuits when everyone else is using square is a pain in the butt. I was called up by a supermarine spitfire at Bundy last year at the air show, he asked my intentions and I was on base, following a Cessna. He then overtook me and cut inside to land before me. I never did find who was piloting it as all the people on their stand disclaimed all knowledge. My slowing down to give clearance from the Cessna was all negated and I had to land long after the spitfire had turned off. I don't know what happened to the dozen or so aircraft following me. Spitfire nice plane, pilot poor quality.

I think the problem in your case was poor airmanship rather than oval circuits.

 

Oval circuits and rectangle circuits should never conflict. You should fly exactly the same distance in both, only the shape varies.

 

 

[facthunter]

Oval circuits.

 

There are arguments for both. The sharp turn onto final can be a health hazard particularly if the base is a downwind situation. All the material put out by CASA, procedures at non controlled aerodromes relates to "rectangular" circuits, so therefore there may some expectation that it is the standard, and I would subscribe to that argument, but retain a bit of flexibility. For instance if you go below a wispy cloud and get your windscreen misted by fine water drops,a circling approach to touchdown is the only way to keep the runway in view to any extent. (looking out the side) N..

 

 

[djpacro]

Reg 166, Operating in vicinity of a non‑controlled aerodrome, is relevant here:

 

..... The pilot ... must .. conform with, or avoid, the circuit pattern ... Note A circuit pattern has upwind, cross‑wind, down‑wind, base and final legs ........

before landing, descend in a straight line starting at least 500 metres from the threshold of the landing runway ...

 

after take‑off, maintain the same track from the take‑off until the aircraft is 500 feet above the terrain ....

 

Penalty: 25 penalty units.

[Guest Cloudsuck]

Reg 166, Operating in vicinity of a non‑controlled aerodrome, is relevant here:

An oval circuit is just a rectangle circuit with bigger radius corners. Still has a downwind, base and final as per the reg. The reg does not state what shape the circuit must be.