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View Full Version : S/E Circling To Land: To Retract Or Not To Retract?


Sporadic E
29th May 2002, 12:44
I did my initial IR test last week (in an Aztec) and did the usual S/E visual circling approach to land, retracting gear/flaps on the go-around as with normal training practice.

However, varied opinions have been expressed to me by various instructors and examiners about whether, in the "real world", gear and flaps should be retracted at all during the S/E circuit.-

e.g.-

- Always do it because S/E performance is so marginal on a multi-engine piston
- Don't do it on an Aztec because it has the S/E performance to cope with gear and flaps down, especially on a training flight.
- Definitely don't do it in an Aztec because the hydraulic pump is on the #1 engine and if the #1 engine fails, it's time for the hand pump!
- Do it on a situational basis (type, weight, altitude, temperature considerations etc.)

So I was interested to know if the forum had any views on this discussion, and if there was a general consensus on the "right" way to do it.

Regards.

kriskross
29th May 2002, 16:50
Our Company SOP's for a circle to land on the 737 are, two engines, flap 15 gear down, one engine, flap 10 gear down.

fireflybob
29th May 2002, 17:14
If I was one engine inoperative on a twin I would only consider a circle to land in emergency - better to divert to an airport where I can fly a straight-in, preferably with a precision approach aid such as ILS.

'%MAC'
29th May 2002, 17:22
In most light twins you simply donít have the power available to leave the gear and flaps out in a go-around. The typical procedure in a circle to land maneuver is gear down at or before the marker and flaps at the max takeoff position (for the 737, flap 15), this configuration is maintained until on base leg when landing flaps are selected and landing checklist is complete. Missed approach or go-around (balked, wave-off, what ever you want to call it) is go-around thrust, rotate to go-around attitude, flap raised to max takeoff (again flap 15), positive rate, gear up, new speed schedule. (Before others start yelling at me thatís from pg 04.70.49 Boeing manual, and it also applies to the EMB-120, the BE-02 is flap 17 degrees but the same procedure applies).

One airline training instructor put it this way, ďEither the missed approach or aborted landing is in reality, simply a takeoff begun at a higher altitude and without the necessity of accelerating on the ground.... Just get takeoff power on the aircraft, get it into a normal takeoff configuration, and then fly as normal a takeoff path as possible.Ē

If you are in the situation of an OEI go-around, have the other person pump the gear and flaps up. (It will keep them busy, alleviating a sense of helplessness from them.) If you are flying single pilot, first try not to get into that situation, if you canít help it, then itís youíre choice to raise the gear and flaps (ainít command great). Iíve forgotten how difficult it is to pump the gear on the Aztruck, if I had the performance and no SIC, I might leave the gear down (considering environmental variables, icing, degree of performance, etc.).

Many training organizations consider the night single engine circle to land maneuver a double emergency and do not train for such eventuality. The thinking is that it is better to go straight in with a tail wind, then try circling with such marginal performance.

Congratulations on your upgrade
:)

411A
29th May 2002, 17:38
Hmm,
if you do find yourself in the unlikely position of having to CIRCLE (in poor wx conditions) with an engine out in a light twin (not an airliner)...would respectfully suggest that you leave the gear and flaps UP until you are in a position to begin your final descent to the runway, from the circling maneuver, ie: downwind or base leg. The only exception possibly would be with a light twin with very good E/O performance ie: Cessna 441, for example.
To do otherwise is foolhardy, IMHO.

Captain Stable
29th May 2002, 18:57
I would never, ever considering leaving any drag at all on the airframe in a piston twin.

Even when flying one that had a good engine out performance, don't even consider it. Because you should get into the habit of "best practice". If you don't, the day you hear a "bang" and feel that yaw is the day you're not going to think about it, but have to revert to training. And sod's law dictates that that will be the day that the prop has actually fallen off, and in doing to has crumpled the wing leading edge just where you can't see. That little bit of extra drag can result in you going in.

Consider that, with the gear down, you've increased the drag just behind your live engine. No asymmetric effect there. But you've also got a wheel dangling right out on the other side, making the yaw even more than you would otherwise have.

Not only are you having to push harder on the pedal just to keep it straight, but it no longer has the authority you'd expect, because with increased yaw you've also increased Vmca. You've also increased your stall speed. Blue line speed is no longer where you thought it was.

Don't assume that even all aircraft of the same type have the same performance. There are some very nice, zippy Aztecs out there. There are also some real dogs.

If you need to crank that handpump, then do so.

There is only one way to do it, and that's by the book (POH).

The best mnemonic I was taught is based on the first word that comes to mind in such circumstances.

Firewall everything
Undercarriage and flaps up
Correct the yaw
Kill the dead engine

Don't stop to think about it - DO IT. If the manifold pressure drops too far whilst thinking about it, you will spend the rest of your life trying to feather the dead one.

RatherBeFlying
30th May 2002, 04:31
You should be aware that there is a certain mortality rate in practice single engine go-arounds in piston twins. I once saw the remains of an Apache that cartwheeled on a practice single-engine go-around. A few years after that, an inspector and candidate died attempting a single-engine go-around during a flight test in a piston twin.

If the instructor/inspector says there's a truck on the runway after the wheels are down in a piston twin, tell him you're landing on the grass.

john_tullamarine
30th May 2002, 05:35
Keep in mind that, for the smaller FAR23 twins below 6000lb, the situation is worse than for those of slightly higher weight due to the certification differences with respect to OEI climb performance.

I may be viewed as a bit of a fraidy cat dinosaur .. but on late final with gear and flap, any sort of reasonable weight ... and only one motor working on a light twin .. especially hot and high ..... missed approach is not a desirable option .. and may be unachievable ... I would much rather thread my way around the surprise obstruction on the ground.

All a matter of putting the risks of one path (continued landing) on the one side of the scale balance .. and the others (the missed approach) on the other side ... I suspect that the accident stats would indicate that more people are killed more often by mishandling such a critical missed approach.

There is no simple or correct answer ..... neither alternative is a pleasant thought to contemplate ... either may kill you .. the best you can do is try to plan to avoid the situation.


Sporadic E,

As to whether you clean up during the OEI missed approach if you elect to go down that path ? .. on this class of aircraft .. if you choose not to .. please do let me know so that I can decline the flight .. light twins generally go nowhere except downhill with gear and flap down ...

I'm with 411A ... go clean (other than for some initial flap if that is appropriate for the circling radius considerations) in the circuit until you are very satisfied that the landing can be assured ... to do otherwise on this class of aircraft is to take a significant gamble ..

OzExpat
30th May 2002, 06:42
I've done a lot of time in Aztrucks and can assure you that they go nowhere but down on one engine, with gear and flap extended. Its not just a matter of getting rid of the flap either. In the classic flight check scenario of engine failure after take-off, with no usable runway left, always get the gear away and consider my flap options.

I say "consider my flap options" because the Aztruck I have most time on was fitted with a Robertson STOL conversion, so the flaps were flaperons. In a standard machine, I'd get rid of the flaps without a second thought.

With the engine failure on approach in the Aztec, I'm going to land, not go around. And, if I have to use the hand pump, so be it. Planning for this will modify the way I manoeuvre to get back to the runway, but I wouldn't be too concerned about using flap during the approach unless I was especially high - and I'd try to avoid that scenario too, if I was you.

I always brief myself on what I'll do in the event of engine failure before, during or after take-off. As part of my forward planning for a landing, I'll brief myself, about 30 miles out, about engine failure during the approach and landing. Then I plan to stick to that plan because it takes account of known weather conditions and as much info as I have on other aircraft in the area.

foghorn
30th May 2002, 21:38
I was always told that in an Aztec with an engine out, the gear and flap levers basically convert it from an aircraft into a piano...

Capt. Crosswind
31st May 2002, 04:13
As previous posts point out performance is marginal even on a good day.
Approach flap is all you should use for circling & landing (or better still flapless if appropriate) which puts you in a better position for the go-around if you must (John-T's advice is my prefered option)
Don't fall for the "full flap when a landing is assured" line.
Every pilot who wound up inverted on the threshold ( and there have been many) did just that.
The best rule I have heard on the matter is -
" Under the prevailing conditions of Weight/Altitude/Temperature
know how well the acft will perform - if it is marginal make sure you walk away from the wreck"

erikv
31st May 2002, 10:58
I agree with most of the posts above. I don't see going-around OEI in a light twin as an option.
Accident statistics show that fatilities are more common after an engine failure in a twin than in a single. The solution? See twins as singles with better glide performance. In an OEI situation, do not select anyhting that increases drag unless you really need it (you'll need the gear for touchdown, but you probably won't need flaps in most cases) and keep in mind that you're just about commited to land once you select it.

To answer your question: If I would need to do a single-engine circling in real life, I would leave the a/c as clean as possible during the approach, selecting only approach flaps depending on the situation. While circling I'd consider selecting gear down while on base or in the final turn depending on travel time in the type involved.

The FAA published two interesting leaflets on this subject in co-operation with the GA manufacturers. They are
- Always leave yourself an out , see http://www.flyboy.nl/fltsafety/APP-8740-25.html
- Flying light twins safely, of which I only have a paper copy


Capt Stable,

I've been taught that (and I believe the linked document mentions it as well) for most light twins Vmca is actually lower with gear down.

Erik.

john_tullamarine
31st May 2002, 13:59
.. if you're so slow in a light aircraft OEI manoeuvring situation that Vmca is a significant consideration .. then you have run right out of all options ....

niallcooney
31st May 2002, 14:21
Guys,

Why is Vmca LOWER with the gear down? Surely it should be higher due to induced drag and pitching moment effects?

Nial

Captain Stable
31st May 2002, 15:32
Since Vmca is defined as the speed at which the yaw and asymmetic thrust overcome the power of the rudder to keep the damn thing straight, it defies all reason that Vmca would be lower with the gear down.

The net effect on drag of gear dangling is an increase, more or less on the a/c centreline. Your thrust is outboard of that. You are therefore increasing yaw with no change in speed.

Therefore, you are having more difficulty holding it straight with rudder.

To overcome the extra drag, you need extra power. Wonderful! More asymmetric thrust, less rudder control.

If that additional drag is enough for the aircraft to give up, throw up its hands in horror and keel over in a small gibbering heap, you will have discovered the hard way that you were below the new Vmca. The remaining engine will then take you neatly and accurately to the scene of the crash.

Therefore Vmca increases with gear down.

You also use up power just overcoming the drag of the gear when that power could rather more usefully be used in increasing your speed to blue line, or in actually getting away from the ground.

Alternatively, if you have power to spare, you could take a little care of your one remaining engine, and lift the gear and give the donk a chance to get its breath. Look after it - all of a sudden it's become your only chance of survival.

Remember:- nobody ever collided with the sky.

'%MAC'
31st May 2002, 18:00
I can see your thinking, but let me explain it a bit different, if I may.

With the landing gear extended Vmca will be lowered. Drag rises as the square of airspeed; the increase in airflow from the operating propeller will increase drag on the landing gear that is hanging in the propeller slipstream. This will be greater then the drag from the other landing gear which is in the free stream velocity. Hence, the drag vector will be displaced more toward the operating engine then with your gear up. This drag vector positioned on the same side as the thrust vector reduces the yawing moment about the CG. Additionally, lowering the gear will increase stability and lower the CG, in some cases increasing the moment arm from the rudder.

Vmca is determined with maximum available takeoff power or thrust, it is a constant. There is no requirement in part 25.149 that at Vmca one maintains level flight, (performance is covered in other places, such as 25.121) hence there is no need or even ability to add extra power. With the landing gear out you reduce your Vmca and you reduce your performance. Two different aminals.

One can think about Vmca as controllability only, whereas Vyse/ Vxse addresses performance

john_tullamarine
1st Jun 2002, 01:12
Vmca is a bit more complex than the definition suggested in previous posts .. involving both a static consideration (can I keep the thing going more or less in a straight line) and dynamic (if one quits under critical conditions, can I keep it under reasonable control without exceeding acceptable excursions in attitude and heading change.

I suggest that it is an unsafe logic to generalise too much about the presumed effects of this and that on Vmca as more than one factor is at play. Certainly, it is not too difficult to come up with a plausible theory as to why this or that effect is noted after a configuration change ... but to predict a generalised result often is unsound.

With gear down, for instance, the drag of the individual undercarriage assemblies may have a useful effect on the initial rate of yaw/roll excursions which may influence the dynamic assessment favourably.

Equally possible, the presence of the undercarriage assemblies may have an effect on the directional characteristics of the aircraft and adversely influence the assessments. One needs to keep in mind that the test pilot is using sideslip to the most favorable extent he or she can (which is why the 5 degree bank limit is in place) and that sideslip airflows may see the wheels (especially the nosewheel - which will be destabilising) as potential lateral lifting surfaces.

%MAC raises the possibility of CG changes with gear having an influence and this could be of significance if, for instance, the gear assemblies are large (eg high wing aircraft with nacelle mounted gear) and the extension of the gear moves the gear assembly masses (and overall aircraft CG) a tad forward. His thoughts on propeller slipstream may be a little too optimistic as he neglects possible effects of the flow circulation which, potentially, could be destablising.

The design standards are pretty basic in respect of OEI handling and performance for light aircraft .. which is the main thrust of this thread. A "reasonable" manufacturer's flight test organisation ought to investigate a particular aircraft's characteristics in somewhat more depth than the minimum requirements of the standards. Whether much of the detail which might come from such investigation ever sees the published light of day is, of course, quite a different matter altogether.

If the data is published, or is determined post-delivery by a competent test program ... fine. If you don't have the data ... it is a bit of a greasy slope to traverse if you try to infer generalised handling responses.

DFC
1st Jun 2002, 15:52
The most important part of your question that I think everyone has missed is;

What you described and what you did on your IR test was not a circling approach.

What you did is an ILS to minima followed by a single engine missed approach which was converted into a visual circuit.

For a circling approach, your minima would have been the circling minima i.e. an MDA(H) and you would have flown level at that MDA to the MAP Pt if not visual. Or you would have flown at that MDA(H) on your circuit to land.

If you have problems maintaining MDA with one engine out then can you shoot any approach in reality?

DFC

Captain Stable
1st Jun 2002, 17:10
Very good point. On a true S/Eng circling approach, of course, you probably wouldn't drop the gear anyway, if you are expecting to see the ground before you hit circling minima. Maybe a stage of flap, but that's all. The rest can wait until sometime on the downwind leg.

Since circling minima are well above ILS minima, this is not a problem. If you can see, you can circle (and cancel IFR). If you can't, you can't. You could continue the ILS and take a downwind landing, I suppose, and if that's your only option in a real-world exercise, that's what you'd have to do.

But a S/Eng ILS to minima with a go-around is a different beast altogether, and I would most certainly counsel getting the drag flap away immediately, followed by gear as soon as +ve climb is established, and then the remainder of the flap.

bluskis
1st Jun 2002, 19:23
Unless you have added a short runway to the list of challenges, why use any flap on approach if you are one engone out on an Aztec, whether it is the one with the pump or the other one. In the absolute necessity to go round its one less problem. Aztec take off configuration is flapless normally.

411A
2nd Jun 2002, 01:44
Interesting point raised about "circling and IFR cancellation."
In the USA, if you are performing an IFR approach where the ceiling and/or visibility are below basic VFR minimums, and the airspace around the airfield is controlled (class D/E for example)....IF the pilot cancels IFR before landing, he would then be operating in controlled airapace below basic VFR minimums, without an IFR clearance.
NOT good, if (for example) an FAA Inspector should be watching/listening:eek:

DFC
5th Jun 2002, 00:51
On the cancell IFR, there is no requirement. As has already been said, in a cat A aircraft, the circling minima will be below VMC in controlled airspace.

IMHO, a circling approach is simply a non precision approach with a very long time spent level at MDA.

I expect that everyone on a single engine non precision approach will lower the gear at the FAF. They will then (subject to step downs) get down to MDA as soon as possible and fly level at that until visual or MAP.

Thus there is absolutely no problem with the aircraft maintaining level flight on one engine. In fact it is a public transport requirement. If the aircraft can not maintain height then the planning minima along the whole route are ceiling 1000ft i.e. one must be able to complete a forced landing and no over water flight is permitted.

In a real emergency the best option is a visual approach. If that is not possible then an instrument straight in approach. A circling approach is a last resort.

Confusion has arrisen because the sequence of the IR test is being confused with a circling approach.

On the test, the examminer will have simulated an engine failure in the missed approach. The correct actions indicate that the pilot can cope correctly with an engine failure IMC in the climb, close to the ground be that in a missed approach or after take-off. This does not test the candidate's ability to fly a single engien approach to appropriate minima and at the appropriate point execute a single engine missed approach.

In order to test the latter, the missed approach for the ILS is flown single engine but terminated as soon as the examiner is happy that the correct avtions have been completed and a visual circuit is completed to land.

This visual circuit is not a circle to land it is merely a means to get the aircraft back onto the ground at the completion of the test.

DFC

john_tullamarine
5th Jun 2002, 06:13
DFC,

You suggest that

"there is absolutely no problem with the aircraft maintaining level flight on one engine. In fact it is a public transport requirement".

As this statement follows directly on from

"I expect that everyone on a single engine non precision approach will lower the gear at the FAF. They will then (subject to step downs) get down to MDA as soon as possible and fly level at that until visual or MAP"

it appears you are suggesting that the two are linked, ie one has a mandated ability to fly level OEI with the gear down ?

I, for one, have missed something here. Could I ask for you to guide me to the requirement which supports your statement , please ?

411A
5th Jun 2002, 07:40
....also watching/listening with eager anticipation....