Climb Gradients and Emergency Turn/Special Procedures

[A4]

The recent thread regarding go around performance and emergency turn has left a few questions in my mind.

The Jepps state that the establishment of emergency turns/special procedures is the responsibility of the operator.
Therefore an operator would employ a third party to survey an airfield and all its associated obstacles to allow a procedure to be
defined.

So:

Are there a set of defined parameters that the design of these procedures must adhere to?

Presumably the designed procedure is such that it avoids the "lumps" and allows the maximum take-off mass (with associated minimum gradient)?

Is the procedure designed with the absolute worse case scenario in mind. ie Max TOW, ISA +35, low QNH etc and the resulting gradient?

Consider the following scenario.

You get airborne and during the climb (well clear of all obstacles) you suffer a fire/failure which requires an immediate return. Under the circumstances, your achievable gradient is only 1.9% so you elect to operate to a (much) higher minima to allow a missed approach to be flown. It's CAVOK :) so you continue below minima but then have to go-around :rolleyes: How do you KNOW that the take-off emergency turn is going to be ok for you at your 1.9% gradient? OK, you're in a better position because you're starting the go around at an earlier point than the take-off failure scenario but where's the guarentee? Do all these turns cater for the MINIMUM (worst case) achievable gradient?

One thing I have learned is that emergency turns do not have any leeway for wind effect.....so if you've got strong crosswind blowing you towards that hill, you better make sure your tack is good.......bank angle....climb performance.....?

If you subsequently fly it into the side of a hill, where does the Company/surveyors/your estate :( sit.........?

If anyone can point me to a link on the web which discusses these procedures/ design of in detail I'd much appreciate it.

In the mean time, over to you all for your thoughts and opinions!

Fly safe,

A4 :)

[FlapsOne]

A4

Not sure I'm understanding you correctly.

Don't know specifically how Emerg Turns are designed by the 'researchers' but think about it practically.

Your perf calculations tell you what weight you can safely take off given the conditions of the day. Some days that might be MTOW, other days less. QNH, temp etc are all taken into account in these calculations.

If an Emerg Turn is specified it must be followed and is certfied for up to the Max allowed take off weight for the day - no heavier.

So you return following an engine failure - if your take off weight was within the calculated max TOW then your Go around will as well. If you can legitimately take off on a runway within perf requirements then you can go around as well (single engine above v1 etc).

If you haven't got the performance for a go around then you shouldn't have taken off in the first place.

Landing weights is a different issue altogether.

Sorry if I've misunderstood your point.

[BOAC]

<Is the procedure designed with the absolute worse case scenario in mind. ie Max TOW, ISA +35, low QNH etc and the resulting gradient? >

Generally speaking, the TOW allowed WILL assume you will fly the emergency turn for E/Out terrain clearance, and will be calculated for the ambient temperature and QNH. Thus MTOW will be lower if the temperature is higher or QNH lower. Most ETs expect you to follow the initial part of the SID (presumably you WOULD adjust for drift there?) or specify a heading, track or turn. All such will allow for a reasonably-to-be expected adverse crosswind. Unless a specific E/Out G/A procedure (eg Glasgow R05) is specified, it is 'safe' to assume you will be ok up to the max allowable landing weight for that runway.

All the above assumes, of course, that your company has got it right!

I suspect you need to look at PansOps in Europe for guidance. I expect one of the 'fundis' on this forum will come up with a link for you soon.

[john_tullamarine]

If the scenario is that

(a) you have just taken off,

(b) had one stop, and

(c) then have to do a miss on the approach,

provided that you are in the previous takeoff configuration and flying at the appropriate escape speeds to constrain turn radius, there is no specific problem associated with following the takeoff escape procedure ... other than for two very important considerations if you intend to thread your way around the hillsides ...

(a) you need to track over the runway head to establish tracking tolerance

(b) you need then to be able to maintain the nominated escape tracking requirements while attending to the climb gradients.

These are not insignificant problems ...

[reynoldsno1]

Therefore an operator would employ a third party to survey an airfield and all its associated obstacles to allow a procedure to be defined

Not necessarily so. International airports have an obligation to promulgate ICAO Type "A", "B" and "C" charts which detail obstacle data around the airport out to different distances. These charts are often used by operators to devise their contingency procedures.

[A4]

Thanks for the answers so far gentlemen. To take things a step further, presumably an emergency turn is only established when either the obstacle in question is insurmountable on one engine or if "standard" Perf A criteria were adhered to the resulting maximum take-off mass would be "commercially unviable" or a compromise of the two.

One again thanks for the replies.

A4

edited for imbecilic spelling........:rolleyes:

[john_tullamarine]

A4,

Sounds like a reasonable summary .....

[mutt]

we have a couple designed to keep aircraft from crossing into foreign countries.....

we also account for wind so that the turn is based on a constant bank angle but the track is adjusted accordingly.

As for doing surveys, we take AIP or Topo data which is then adjusted in height to account for the loss of climb gradient in a turn.



Mutt

[john_tullamarine]

... but, on occasion and if it be necessary or otherwise desirable to have a day out of the office, we either commission some survey work .... or throw a theodolite over the shoulder and take a buddy out and do a spot of surveying to resolve the odd discrepancy in the available data .....

[OzExpat]

Better you than me, j_t! :D

[Menen]

Flew for large European charter company once. The emergency turn specified in the company ops manual (B737-400) from a certain Greek island, required a turn through 90 degrees at runway end and a few seconds later you were over water. Flap retract was promulgated as 800 ft. No further info supplied so you assume you are safe. Problem was an island 10 miles dead ahead on emergency turn heading with spot height 1500ft.

The acceleration segment took you into the spot height. When questioned, the company performance engineers stated that the surveyed area stopped short of the island but was perfectly legal and that it was up to the captain to use airmanship to avoid the spot height.

Makes you wonder how many other take off obstacle charts leave the pilot in the lurch because the pilots are not advised of the length of the surveyed distance, and rely totally on the performance engineers to keep the aircraft safe. Often a case of misplaced trust. Of course it only matters if an engine stops after V1!

[john_tullamarine]

Menen highlights a standard problem .. just what do the ops engineers include or not include in an escape procedure ... if the ops manual is not explicit, then that suggests that the flight department needs to do some homework so that the line troops know the score ...

[OzExpat]

:eek: The same situation could just as easily exist anywhere, whether a turn is required or not. I'd be a tad concerned if there wasn't at least a warning about it in the company docs. It's easy to say that there's no need to survey beyond the legally required dimensions, but I'll bet that the phrase "duty of care" would be uttered during the subsequent inquest!

[RAT 5]

JT and others.

Working for a few airlines, without an in-house performance guru, I found this matter a very grey area. There was nobody who could answer the many such questions raised.

e.g. with one MTOW performance provider there were no notes as to how the data, and ET's had been calculated. When in the sim', and performing an ET requiring various turns, the crew still elected to accelerate and clean up at 1000'. This of course now changed the radius of turn and reduced the climb performance. I didn't think this was a good idea, but no where could we find an answer, and no-one in the company had an opinion. Incredible.
I was applying the philosophy that I'd learnt from Jeppe at another company.

Gues what! We then transferred to Jeppe and there it stated that the ET was for 15' bank at V2 - V2+25, and the flap retraction HT. Quite clear.

However, less clear was the sometimes specified HDG??? If you are avoiding the lumps, and start the turn at a specified point, surely you need to fly a TRACK to ensure clearance. Sadly no-one in the company seemed to be concerned to find the answer. At least we'd cleared up the clean-up technique, though.

There was another company that had the idea for N-1 G/A's. Below max LW fly normal G/A, above max LW fly the ET. Further, they had it that during the ET, take off or G/A, you could accelerate after the first turn of the ET. There were one of two runways where I was very sceptical of that idea. there was still some concrete stuff in front of the nose.

The idea about the spot HT 1500' at 10nm. Remember that the take off performace considers obstacles upto 1500' above the runway. (correct?) How far away is another matter. Anything above that, (The Alps) is for Mk1 brain. Jeppe, for the last company took it out to 30nm. I thought it good idea, unless visual and returning, to climb to sector 25nm MSA and then think about it.

[john_tullamarine]

Rat 5,

Absolutely .. if the chart is lacking in procedural detail (presuming that the company ops manual doesn't include a bunch of "standard" techniques) then the chief pilot ought to be jumping up and down to get the thing corrected and republished.

Keep in mind that many, and possibly most, ops engineers don't have an operational piloting background .. this makes it very, very hard for them to think like a pilot and provide pilot-speak procedures .. ops engineers with a dual background, though, are a bastard creation and think neither like an engineer nor a pilot .. but often can produce useful escape procedures which the line pilot can use in anger without too much head scratching .... something about walking in a man's shoes ?