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Old 6th Feb 2012, 15:33   #1 (permalink)
 
Join Date: May 2009
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Question Working out new MDA/DH with an engine inoperative

Hi,

To work out a new MDA/DH with a CR-2 Whiz wheel what heights do you use?

I know for a MAP you must meet the 2.5% climb gradient requirement.

Therefore before flight you work out a one engine inoperative possible gradient.

Say you worked out you could achieve 2% with one engine.

You would then put 25 (2.5%) below 20 (2%) on your whiz wheel (required on bottom).

You then need to find the required height to achieve the MAP, I am wondering how you work this out. Is it merely the Height given to climb in the MAP on the plate from the normal MDA? (so MAP height - normal MDA height) ?

Just was re reading an example out of a text book without a great explanation.
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Old 6th Feb 2012, 17:04   #2 (permalink)
 
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Dunno 'bout the book, but in real life you're not required to work out a new MDA/DH. The max landing weight is certified to meet all regulatory requirements with 1 engine inoperative, including missed approach climb.

If a particular procedure requires a different MDA/DH for a specific category or configuration of airplane, it will be noted on the approach plate.
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Old 6th Feb 2012, 18:03   #3 (permalink)
 
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That's not true for all jurisdictions. Australia, for example, requires asymmetric performance to meet the 2.5% missed approach gradient *or* adjust the MDA upwards to allow for the reduced performance gradient.

This seems to be the case for this question.

Last edited by Tinstaafl; 6th Feb 2012 at 23:04. Reason: Speling errerrs
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Old 6th Feb 2012, 18:15   #4 (permalink)
 
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Yes my questions relates to Australia, being that it requires 2.5% gradient in the MAP even with one engine. I was thought how to calculate what to add on with the whiz wheel as explained above. But I've forgotten exactly where you get the "height required to achieve missed approach" so once I have the 2.5% under and lined up with the 2.0% on the whiz wheel I can go across and read above this height which will give me the 2.0% value. I then am able to work out the difference in heights between the two and add that figure onto my MDA. But I am not sure which height to use...any one know for sure?
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Old 6th Feb 2012, 23:24   #5 (permalink)
 
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Intruder,
Quote:
The max landing weight is certified to meet all regulatory requirements with 1 engine inoperative, including missed approach climb.
Please stop spreading such misinformation to others including your crews...
Ever checked for altitudes other than the standard sea level???ever checked with use of EAI?landing below 10c ?
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Old 7th Feb 2012, 19:07   #6 (permalink)
 
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Where is the misinformation to my crews?

In context, the regulatory requirement for US certified airplanes is FAR 25.121(d). The airplane must meet the regulatory requirement for one-engine-out performance, which is 2.1-2.7% gradient for the missed approach climb, depending on airplane type, at max landing weight, as I stated.

The base regulatory requirement for the approach procedures is FAR 97.20, which refers to FAA Handbook 8260.3, TERPS. Sec 7, par 270ff specify the regulatory requirement for designing approaches. Note that the approach must be designed to meet the 2.5% gradient of obstacle clearance from the DA or MAP.

The regulatory requirements regarding adherence to the DA/DH or MDA are in FAR 91.175(b)-(e). There is no reference to recalculation of a published DA/DH or MDA.

Sec 5-4-5, par a.4 of the Aeronautical Information Manual discusses changes to approach minimums when "annotated on the approach chart." There is NO discussion of pilot recalculation.

So, if both the airplane and the approach meet the regulatory requirements, the published DA/MAP for the airplane category is valid.

There is NO regulatory provision that I can find that requires a pilot to recalculate a different DA/MAP than that shown on an approach plate for his type aircraft. If you can find such a provision as a regulatory requirement, please post it.

So, once again, while you may do a book exercise in school to figure out the difference in initial altitude for a 2.0 vs 2.5% gradient to a given target altitude in 15 miles, there is NO regulatory requirement to do such a calculation while flying or planning a flight.

Quote:
Australia, for example, requires asymmetric performance to meet the 2.5% missed approach gradient *or* adjust the MDA upwards to allow for the reduced performance gradient.
Doing such a calculation in the cockpit after an engine failure seems to be an exercise in distraction from flying the airplane.

Are Australian operators also required to publish missed approach gradient performance information it the Operating Manual, Performance Manual, or Quick Reference Handbook? US operators are NOT required to do so, so I would be unable to do such a calculation if I lost an engine enroute to Sydney.

Alternatively, do Australian operators publish a maximum landing weight for one-engine-out operations so the regulatory gradient is accomplished?
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Old 8th Feb 2012, 02:42   #7 (permalink)
 
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Australia has numerous differences to US rules & regs, one of which concerns one inop. missed approaches. The rules state, in part, that the approach must not be commenced unless the 2.5% missed approach gradient can be met *or* adjust the MDA accordingly.

So, no, the pilot is not expected to calculate it during the missed but prior to commencement of the approach.

To continue with another example that something you wrote made me think about, Oz rules require multi-engine IFR aircraft to have at least a 1% climb gradient at 5000' ISA when asymmetric, unlike the US where certain Part 23 aircraft may only require climb performance 'be determined'. In Oz this has often meant a restricted MTOW, referred to as the IFR climb weight limit. VFR requires the lesser ability to maintain altitude so even then there can be a reduced MTOW compared to the same aircraft operated under US registration.

Oz used to have its own aircraft flight manual that had Oz specific performance charts. The Oz flight manual is now defunct. Since leaving Oz I haven't really kept up with changes since then so what data is now presented could well have changed.

Last edited by Tinstaafl; 8th Feb 2012 at 03:04.
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Old 16th Feb 2012, 12:10   #8 (permalink)
 
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If its of any help I use a quick rule of thumb for such problems. It goes like this: If for missed approach I must achieve 2.5% climb gradient all you do is multiply your ground speed x 2.5 to obtain required rate of climb. In this case lets assume my ground speed to be 120kts so 120 x 2.5 = 300fpm required. Simple! Rules of thumb are on the go in seconds simple calculations. Not only for gradients of climb but also for degrees of climb. Suggest to learn more about it here only if you care.
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