"Drift down" jet circuits in a CTAF under NAS 2C

[ITCZ]

Following on from a discussion in this NAS 2C post (http://www.pprune.org/forums/showthread.php?s=&threadid=199646&perpage=20&pagenumber=2) .

I don't see why I cannot do a drift-down circuit in a CTAF or a CTAF(R).

Capt Claret said Another NAS2c cost saving has become apparrent. Due to the not above 200 kias, and level circuit requirement, 717 circuits now flown with slats extended and signifficant power on, rather than the driftdown in the circuit and reconfigure at idle thrust that had worked quite well for ..... years.

In reply, F/O Bloggs gave the details of his call to the NAS Hotline to find out what their thinking was.

However, my reading of the new procedures says that we can still fly a drift-down circuit.

My references are Jepp, apologies to AIP folk. Italics and bold are mine.....

ATC 6.2.1.3
Aircraft should not be operated in the circuit at an indicated airspeed of more than 210 knots.
("Should not" instead of "Shall not" or "Must not.")

ATC 6.2.3.1
When operating at non-towered aerodromes, the following circuit heights are recommended:
a. jets/turbo props/high performance aircraft; 1500 ft AGL.

ATC 6.6.5.1
Entry of the circuit depends upon the direction of arrival and traffic conditions. The recommended methods for entering the circuit are as follows:
a. From the live side, arrive at the appropriate circuit altitude before entering the circuit......
b. From the dead side, arrive at the appropriate circuit altitude before entering the circuit......


OK. When the AIP/Jepp has a requirement, it says "shall" or "must" or "required," etc.

"Recommended" is not a requirement. A recommendation should be followed, but does not preclude me doing something else, if I have a compelling reason.

Here are my reasons for deviating from the "recommendations:"

First up, it ain't just about altitude. The 1500' AGL B717 circuits that Bloggs and Clarrie refer to are flown at a downwind spacing of 1.7 to 2.0nm. That is a lot wider than the 0.5 to 0.75nm spacing "recommended" for piston singles (Jepp ATC 6.2.1.5)

So a C172 or GA8 on downwind is not underneath my flightpath, he/she is inside and underneath me. Likewise for that C402 or Chieftain. So I am not descending onto him/her.

Second, when I join downwind, I am about 8 to 9nm to run to touchdown. We use a 3nm final, a 1.7 to 2.0nm downwind spacing (so thats about the same for base) and the join from the live side at 45 or the dead side at midfield crosswind means a 4 to 5nm downwind leg. So the 500 AGL and 1000 AGL circuit traffic is inside me all the way around.

Third, why did the NAS team feel compelled to use a military crew instead of an airliner crew, in a 1950s 707 flight deck that even a 146 pilot would regard as a relic? Mr Boeing and Mrs Airbus have gone to a lot of trouble to fit computers that work out the most economical descents for bean-counter driven airlines.

All of a sudden a couple of visual approaches in a dinosaur sim, crewed by military pilots disproves thousands of hours of effort at Long Beach, Seattle and Toulouse? Get a grip!

These aeroplanes fly best in a descending circuit. Other traffic is easily seen. In a conflict situation, a faster aeroplane will see the slower aeroplane first -- that is straight trigonometry. Why not allow the crew of the faster aeroplane to descend and configure on schedule, making maximum use of the automatics so they can keep their eyes out of the window?

Thoughts?

[OzExpat]

That sounds good to me ITCZ, as an interested on-looker from overseas. It occurs to me that the same thinking could be used by piston-powered pilots who want to use a 4-times or 5-times profile, to reach their 1,000 feet point as economically and comfortably as possible, without the possibility of frightening their pax with the perception of a low level circuit and radical maneouvring - as in the 25-30 degree banked turn (well, you know what some pax are like in that regard!).

It occurs to me that this would be no more dangerous than the current situation. It would, however, afford an opportunity for better forward visibility for pilots and that has to be better for a good safety outcome.

I'll happily stand corrected if anyone can demonstrate a reasonable case where this might not be as safe, but I think you've got a good idea.

[Capn Bloggs]

ITCZ,

But your ops manual says "must" enter at 1500ft. :ok:

Agree with your comments about the military trialling something they've never heard of before, let alone done. After all, they aren't the best big jet operators in the world... :(

The 1/2nm circuit spacing for a lighty is nonsense. Perhaps the RAAFy 707 drivers or officer Woodward came up with that one. Even in a 150, you cannot do a "normal" 180 turn onto final from 1/2nm spacing. I think most lighties would be a lot further out than that so they could well be mixing it with you in your SNT.

I've been doing driftdowns since 1987 and I'm not convinced they are that much more cost effective. After all, you're only burning the EXTRA fuel from being descending as opposed to flying along level fro maybe 2nm. A few kilos maybe. You'll have to have the slats out anyway (max 200KIAS) and IMO, being level, not thinking about anything inside will allow much more time to be spent outside, even if the FMS is doing the whole thing for you. I just don't think that the costsaving of a driftdown outweighs the reduced lookout and increase in crew workload.

Also, Mike Smith (NASIG), was at pains to tell me, some time back, that although NAS 2c is littered with "recommended" this and that, IF you don't and you have a bingle or incident, they'll hang you for not "ensure(ing) that the aircraft does not cause a danger to other aircraft in the vicinity of the aerodrome", being the new CAR 166 2b. That's why that paragraph was put in there.

If we are really to save fuel, we should be complaining about this turning at 2000ft against the circuit or this stupid 45deg departure manoeuvre.

[Sunfish]

Capt Bloggs, they'll only get to hang you if you survive.

As I've said before, I'll be singing like a canary, but that's not going to protect me from some brain dead trike driver with no radio.

[greybeard]

Prior to, and probably after "that date" in Aviation, F-28s were approved to do drift down circuits from 3000' at the beginning of downwind.
The Fokker has no leading edge devices, saved as I recall 100kg per sector, did not cause any confliction at busy places like KNX/AYE in the days of MBZs and FSUs(fond memories??), we just called what we were doing to the traffic affected. We also did this at towered places PHE/KTA with approval from tower.
It would appear common sense and AIRMANSHIP will prevail at the time in the air, it's the sodding rule makers who need to be taken out and shot.

Cheers

[ITCZ]

Yes, the old Ops Manual! Well, thats life on the payroll - "Do it this way..." If it can be done 'that way' then thats how we do it :)

As for CAR 166, can anyone point me to the amendment that supports the new circuit changes? The CASA 1988.pdf shows Amendment 2, 2003 for division 2.

Bloggs, I'm not sure what you mean by 'reduced lookout and increased crew workload.' Our new ride has a most excellent PROF (VNAV for the 21st century :ok: ) function that flies a perfect drift down right to the touchdown point. This is where I am coming from. There is some excellent automation that can be used to maximise 'heads up' time. Program the arrival way back prior to T/D and let the aeroplane manage the profile during the approach, and open up some brain space to deal with the aerodrome traffic.

It is also a lot nicer for the folk in Row 24 to not have the engines spool down, spool up, spool down, spool up...

[Capt Claret]

ITCZy

What a mine-field huh?!

I agree with your comments that there are lots of recommendations and few mandates, in either the DOTARS guide or AIP (Jepps). You have I believe, ommitted the most important get out of jail (gaol) quick card. Jepp ATC-717 (I kid you not), Para 6.2.1.1, to whit. Pilots should fly a circuit commensurate with the aircraft type they are operating. However the use of any circuit procedure does not alter the responsibility of each pilot to see and avoid other aircraft. Pilots operating in the circuit should manoeuvre to follow traffic ahead of them in the circuit.

Whilst I believe that being recommended probably gives mandate to fly a circuit commensurate with the type flown, I also believe that Mike Smith's warning/comment to Bloggs, re hanging us if we don't comply and there's a bingle, is real CYA material.

Sadly, I am also of the opinion that to disregard the recommendations, in the absence of a safety oriented need to do so, is to operate against the spirit of the procedures. My opinion shouldn't be interpreted as approval of the procedures, as they seem to me to be of no practical benefit what so ever, rather, change for the sake of change.

The DOTARS guide, at Departure Procedures, says, my info in brackets. If departing to the live side (AMAV to ML then north), climb on the extended runway centre line straigh ahead to circuit height before turning, to provide greater lateral separation from circuit traffic.

When past the departrure end of the runway and at circuit height make a 45 degree turn to the left. Continue the turn when clear of circuit traffic and proceed on track outbound.

Does this mean that if there is no traffic I can once again turn at 500 agl to more efficiently set course? Or, do I have to keep heading the wrong direction with flap/slats extended until I can turn, and then often have to track back towards the field to meet the 5nm set course requirement?

[Capn Bloggs]

New CAR 166 (http://www.casa.gov.au/rules/changes/2005/sli243.pdf)

[F/O Bloggs]

Some points to ponder-

- The NAS Hotline lady said that Qantas have advised that they will not be doing the drift in methods but sticking to the drift down method.

- Qantas are hell bent on saving fuel- That is why the boeing and airbus crews descend from their cruising mach no into 285kts or there abouts. Even 100kg of fuel is worth saving on a regular basis.

- I am not suggesting that saving fuel overrides safety of operation, but I am suggesing that it is not safer to operate the drift in method. Nose up attitude in the circuit level at 200 kts is about 8 degrees in the 717, not the best for acquiring traffic visually below you.

- The latest FMCs are designed to Vnav to a 3 deg profile.

Cheers

Bloggs

"Clear Left, Front, Above and to the right"
"BREAK RIGHT BREAK RIGHT!!!!"
:eek: :eek: :eek: