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Old 1st Nov 2008, 20:47   #1 (permalink)
 
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Minimum Climb Gradient with no published SIDs

Heh Guys,

I got a question that came up recently in the office. When departing from an airfield that has no published SID's or DP's what is the minimum climb gradient that will keep you safe from terrain ( is it the 2.4% as per certification of a/c?) and how far lateraly do you have to maintain it to remain safe (MSA extends to 25nm?).

Is the airfield surveyed for obstacles in all directions when no SIDs exist? What procedures would you adopt in this situation when visual cannot be maintianed after rotation?

thanks in advance.
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Old 1st Nov 2008, 22:43   #2 (permalink)
 
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Depending on the country youre in, I'm not sure there is one. Aircraft performance reqmnts are different to that for airspace procedure designs and if a gradient is not expressed, its either 3.3% or 2.5% for a MAP

These airports in my limited experience are all on the coast, ie no terrain when you climb out to sea.

So, either turn out to sea and know your safe, or you can either climb to remain visual until above the 25nm MSA (usually very low seawards of the coast), climb outbound above the DME steps on a suitable track if there are any, or alternatively follow the single engine escape procedure for that RWY which will get you safely above MSA or into a hold somewhere.

Someone else may enlighten us both further.

Cheers
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Old 2nd Nov 2008, 03:32   #3 (permalink)
 
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TERPS or ICAO Doc 8168 Vol 2 specify 200 ft/nm or 3.3% on a random route departure (TERPS terminology) or omnidirectional departure (ICAO Doc 8168 terminology) up to the first minimum instrument altitude. States may file exceptions, but I think rarely do so for this issue. But, the UK does use 500 feet for the end of Zone I instead of the standard 400 feet or 120 meters.

GF
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Old 2nd Nov 2008, 03:43   #4 (permalink)
 
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Interstate so have no reference available, but in Oz AIP's state terrain clearance after take off to MSA is the pilots responsibility (if I recall correctly). Personally would orbit the field till reaching MSA.
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Old 2nd Nov 2008, 07:57   #5 (permalink)
 
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Quote:
TERPS or ICAO Doc 8168 Vol 2 specify 200 ft/nm or 3.3% on a random route departure (TERPS terminology) or omnidirectional departure (ICAO Doc 8168 terminology) up to the first minimum instrument altitude. States may file exceptions, but I think rarely do so for this issue. But, the UK does use 500 feet for the end of Zone I instead of the standard 400 feet or 120 meters.
So all hills and mountains are levelled around airports until they meet a 3.3% gradient then!
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Old 2nd Nov 2008, 08:23   #6 (permalink)
 
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Good Point!
Many airports aren't served with MSAs, or approaches, ect...so the first 'safe' altitude is an airway. Personaly, I have literaly gone to VFR charts for TOPO info, and ofcourse coming in, I get a lay of the land to figure out which way I will go when departing later on, at night, and in bad weather. Needless to say, domestic US, uncontrolled airspace, in the mountains...all that is neeto, but I still climb like hell...once on radar, radio contact...definately feels better.
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Old 2nd Nov 2008, 09:48   #7 (permalink)
 
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Mr Checkboard

Is your answer in jest? If so, OK

But, if not, the question was if no gradient is specified and, I believe, I gave the answer for the two commonest regulatory briefs. If I am in error, please correctme.
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Old 2nd Nov 2008, 21:47   #8 (permalink)
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An important thread, I suggest ..

what is the minimum climb gradient that will keep you safe from terrain ( is it the 2.4% as per certification of a/c?)

2.4% refers to twin gross OEI .. such figures are minimum airworthiness Design Standard climb requirements and have NOTHING to do with terrain. Rather they impose a requirement for the aircraft to have, at the least, a modest climb capability over and above that which derives from curvature of the earth.

The answer is "whatever you need for the particular runway departure?.. ie each runway needs to have an analysis for the particular aircraft Type and Model. Rules of thumb may give you some comfort most of the time .. but there will always be exceptions to the norm. The need is for the RTOW to be restricted as, and to the extent necessary, to make the required climb profile for the runway. Strictly, gradient alone is inadequate due to the OEI climb's segmented nature - including the third segment acceleration and reconfiguration.

and how far lateraly do you have to maintain it to remain safe

The obstacle profile consideration is confined to a defined splay which you can find in your particular operating rules .. however, work on the basis that it is a fairly narrow trapezoid within which you need to remain. Ian Cohn did an interesting study years ago when he was with CASA (then DCA) .. he analysed a wealth of sim data and plotted the actual flight path tracks with an early engine failure .. a small, but significant proportion, of the departures tracked outside the trapezoid ...

MSA extends to 25nm?

The problem is the distance needed to get to MSA OEI ... eg, for a limited twin you can be looking at upwards of 50 miles to get to 1500ft .. let alone MSA. If the work is to be done appropriately, it is not a simple matter for complex terrain airports. Hence the usual desire for turnback procedures to reduce the terrain data gathering exercise

Is the airfield surveyed for obstacles in all directions when no SIDs exist?

Yes .. and, no. The typical aerodrome charts provide some information (often enough except for the more interesting aerodromes).

Some reading here and here

What procedures would you adopt in this situation when visual cannot be maintianed after rotation?

You do an instrument departure. The AEO/OEI procedure/tracks are defined and obstacle considerations have been addressed (for the better operators, at least). In respect of trying to wing it visually when you have terrain to worry about ... not worth trying due to the shallow climb gradients achieved in limiting conditions.

As others have suggested, not all operators do a good job in this area .. I can recall one, at least, which just ignored terrain ... working on the basis of runway limits only and AEO for the climb.
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Old 9th Nov 2008, 13:28   #9 (permalink)


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Lightbulb

The chances are that, for anyone who is looking for a real answer to this question... there is...




NONE!


If you venture into the developing world without company procedures for departure, I feel sure we'll all read about you in the fish wrappers. If you don't want to feature in there, along with 200+ pax who trust you, don't go to those places if your company doesn't already have an OEI escape procedure.

There are lots of folks like j_t who can provide the necessary expertise to keep you (and your 200+ pax) safe.
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Old 10th Nov 2008, 02:00   #10 (permalink)
 
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John and OzExpat, while I understand the airlines will have analysed the options to the Nth degree, what about the IFR charter guy in his Chieftain, or for that matter, a jet charter operation.
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Old 10th Nov 2008, 04:28   #11 (permalink)
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airlines will have analysed the options to the Nth degree

unfortunately, some don't .. and others think black and white rather than operationally

what about the IFR charter guy in his Chieftain, or for that matter, a jet charter operation.

for the lightie driver .... as the CASA FOI (who drove the change to the rules some years ago to require the GA IFR driver to consider terrain) advised me (with a straight face) .. the pilot can do the sums from the POH data using the declared aerodrome gradient data. Nice guy but, after a period of pointless discussion, I just had to shrug my shoulders and give up Realistically, the pocket rockets are reasonably well off .. the Aztrucks and Chieftains require a bit of finesse ... which, quite often, is outside the technical ambit of the pilots concerned. What is the solution ? Can't say that I can see one in the current regulatory structure.

if the jet charter is subject to CAO 20.7.1b .. then the same rules apply as for heavy iron.
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Old 10th Nov 2008, 04:35   #12 (permalink)
 
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Technically speaking....

Checkboard has it right...if your at a VFR airport, your on your own for terrain clearance...and when you do that trying to get ahold of ATC, in the clouds, you will be asked to 'maintain your own terrain separation through X altitude' That said, if you got in, you can get out...VFR, and it you can't get out VFR, in uncontrolled airspace...it's nice to have taken a good look at the property when you came in, so you know which way your leaving that night in IMC. Needless to say, some VFR terrain type charts, climbing right over the airport or right to a navaid, or airway, like a bat of hell to the nearest, closest, lowest piece of protected airspace is how I do it.
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Old 10th Nov 2008, 12:17   #13 (permalink)
 
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What about a bit of map study... excellent 1:50 000 maps are available for pretty much everywhere.

I was trained BGPS (before GPS) to draw a line and then apply terrain clearence in an expanding cone from origin to dest. It was pretty time consuming but your safe altitudes/levels were your responsibility - thats why you got wings..

It might not satisfy FAA, JAA, et al but will keep you out of the rocks and is far better than blasting off into the "unknown"
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Old 10th Nov 2008, 23:06   #14 (permalink)
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excellent 1:50 000 maps are available for pretty much everywhere

Better than nothing but would need to be applied very conservatively. Map errors/omissions remain a major concern.
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Old 11th Nov 2008, 10:11   #15 (permalink)
 
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Quote:
unfortunately, some don't .. and others think black and white rather than operationally
So true.
One airline I worked for mentioned...OEI, climb straight ahead to 1500 agl...no problem.
When I mentioned that this would be a rather bad idea at some airports, I received, in return, that deer-in-the-headlights look from the respective fleet manager.

He learned quickly...better be prepared with obstacle data, otherwise you can become dead meat in a hurry.
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Old 11th Nov 2008, 11:04   #16 (permalink)
 
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Good thread. I always like to know the ft/min that equates to the required gradient (s/e speeds) , before I start the take-off roll.
One thing I do wonder about is the start of the third segment and the priority it should be given. On the 737 my company SOP is to bug the aceleration height on the altimeter for the particular runway, so that if you lose an engine, then that height is where you begin the third segment. Through discussion at work I realise that some pilots would continue the second segment until they had completed any recall actions, while others would accelerate at that height as they reached it regardless of workload. I would be interested in everyones thoughts on this as I am in two minds, especially if the departure is over water. If there is terrain ahead then I would be accelerating at the specified height.
Cheers, Framer
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Old 11th Nov 2008, 11:55   #17 (permalink)


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Sorry to burst the bubble framer, but the reality is that sooner or later even the water ends. But what about the things that float and, Heaven Forbid, even DRIVE across the very same water that you plan to fly across at "ZOT" feet? The average "junk" probably won't even present a problem for a Chieftain, but a small coastal freighter could be a pretty major problem to a cargo 727 or just about anything else that loses an engine at or just after V2 (I'm not getting into specific arguments about V1 because I've already seen too many people die when they went for something that was well beyond their abilities).

411A is right, though I wish there were more people of the like that he's described. I have to say (not that I NEED to do so) that j_t is spot on. There really are NO guarantees for the poor bloke who's stuck in the non-performing light GA twin. There's a major difference between FAR 23 and FAR 25 and, if you don't understand the difference, you better study it because the aeroplane you fly will be certified under one or other of those FARs.

What say you, John?
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Old 11th Nov 2008, 12:29   #18 (permalink)
 
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But what about the things that float and, Heaven Forbid, even DRIVE across the very same water that you plan to fly across at "ZOT" feet?
Righty-oo then....Not really planning on flying anywhere down low like that Oz......anyway,

The lowest acceleration height we use is about 500ft. Maybe I didn't make myself clear, I'm talking about the height at which you cease maintaining V2 and accelerate to clean speed. eg if you were departing over water, (lets make it 1400nm of water so Oz doesn't worry about it ending,) and got severe damage to an engine. If the acceleration height was 600ft, would you a) accelerate at 600ft whilst carrying out recall items or b) finish recall items and then accelerate.
Cheers
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Old 12th Nov 2008, 01:04   #19 (permalink)
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One thing I do wonder about is the start of the third segment and the priority it should be given

Same priority as the other bits of the procedure ?

Often the third segment is limited by the engine limit .. ie push the acceleration higher and you push out the 5 minutes. In the very occasional event that the failure is real, it probably remains academic.

I can't ever recall having looked specifically at arbitrarily increasing the accel phase for a straight ahead flight path .. although I would expect that it would not routinely present an obstacle problem.

HOWEVER, if there are any TURNS in the procedure, then the crew had best follow the procedure fairly accurately as the turn radius - hence trapezoid coverage - depends critically on speed - which is linked to the configuration. A planned second segment turn at V2-ish sees you over totally difference terrain if you are accelerating to final climb speed during the turn.

Apart from the IAs for a major problem (fire and severe damage types of problems), there is probably no real urgency to do the systems drills in preference to flying the aircraft .. why not just fly the procedure and then, when the procedure workload permits, worry about the switches and PAs, etc. It seems to me that the main risk in this situation is running into some cumulo granitus so that is where the risk mitigation efforts ought to be directed ?

Unless things have changed in recent times, if I think back to 727/737 it was never a problem to fit the drills into the flying .. indeed, periodically in the sim we would do the OEI departure exercise single pilot just to put a tad more load on ourselves for practice... the workload was never a problem (unless one's mate in the back seat started playing the organ to relieve his boredom ?)
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