Climp gradient

[C340]

Dear all,

I have recently flown into Thessaloniki, Greece RWY 10 an ILS DME procedure. Now my quastion is : for DA there are two different altitudes with significant difference of 400+ ft. This is due to a different climb gradient set, one with 4.0% and the other with 2.5% min.

How can you calculate what your climb gradient is in % and in ft/ min???

Thanks

[High Speed Descent]

Rate of Climb = Gradient x Ground Speed

so,

Gradient = RoC/ Gs

[oldebloke]

one percent is 60' per mile(knot)ergo 2.5% is 150' per nautical mile x G/S(120mph=300' rate o' climb)
4%=4 x 60'=240 per mile x G/s 120=480'rate o'climb.:ok:

[JABBARA]

Some more,


Sometimes gradients are expressed as Feet/NM. In this case to convert to gradient to percent (%) form:

% Gradient= (feet/NM)/ 60.


Example: 420 feet/NM gradient equals to:

(420/60) %gradient. I.e equals to 7% gradient

[Cuban_8]

All good stuff i'm sure guy's, but not very practical when you have to use the information for real in anger!

The standard ICAO required MAP gradient is 2.5%. Where an increased gradient is necessary for terrain purposes, this will be stated. However, minima are still published for the standard 2.5% gradient, abliet with a higher value.

I suggest that you refer to your AOM or Performance manual, where the achievable Landing Climb and Approach Climb gradient will be published according to configuration, weight and environmental conditions. You are then in a position to select the appropriate minima, considering the possibility of a donky failure at any time, of course. Always have an escape route!

Regards,

Cuban_8

[Old Smokey]

C340, your profile doesn't indicate your aircraft type, but I'm guessing that it's A340 from your call-sign. I don't fly the A340, but I'm assuming that, like most other aircraft of it's generation, that it does have Flight Path Indicator / Flight Path Vector Indication. FPV is indicated in degrees, and to convert from Gradient in % to degrees, multiply by 0.6,

e.g. 5.0% X 0.6 = 3.0 Degrees

If you then fly to, or observe as a minimum the FPV you will meet the requirements.

NOTE - 0.6 is not quite correct, but very very close and slightly on the CONSERVATIVE side, the 5.0% used in my example is actually 2.9 Degrees.

I regularly use FPV to satisfy Gradient requirements in SIDs, and for Non-Precision approaches where a Descent Gradient is quoted. Being Inertial it's extremely accurate and instantly responsive.

The problem of dual minima into Thessaloniki that you quoted is one that we often see into, for example, Hong Kong 25R, where the (Right Turn) missed approach is over very high terrain, and the ILS DA very much higher if unable to meet the gradient from the normal DA (I don't have the chart with me, sorry, no figures). My operating policy is to refer to the AOM/QRH to ascertain climb gradient capability, and if unable to use the 'normal' DA, operate to the higher DA. If a missed approach after the DA should become necessary (loss of visual, engine failure etc.), operate to the (Left Turn) Engine Failure Escape Route.

[mutt]

Old Smokey.

For HKG, it the MAP gradients are both higher than standard, do you reduce your arrival weight to ensure that you can make whichever gradient you plan to use?

Mutt.

Nice to be back.. NOT..... Offer of beer still stands next time you get here :)

[Old Smokey]

Mutt,

Our computerised Flight Planning considers RTOW for the departure environmental conditions, and specific to the runway and obstacles (of course). For arrival the normal Structural and Field limits are considered, but unfortunately only the 'normal' Approach Climb / Landing Climb is considered. It is incumbent upon the pilots to ensure that landing weight is not more than that to achieve at least the LOWER of the MAP gradients available (based on forecast conditions). Approaching HKG when actual environmental conditions and landing weight are known, the approach minima to be used is decided upon. Fortunately, due to the great number of nearby alternates, fuel on arrival, and therefore weight, is pretty low, and usually no great disadvantage presents itself. The Typhoon season is another story!

From a PERSONAL point of view, I'd have no problem going all the way to the 'normal' minima, and using the OEI escape route instead of the published MAP, but the rules are the rules are the rules.........

The powers of darkness continue to keep my roster 'off optimum', and a performance commitment in a southern continent continue to control my life - keep that beer well chilled, I intend to accept the offer.

It IS good to have you back, it was bleedin well boring without you.

Smokey

[C340]

Thanks to all... as for the aircraft type is a 737-300.

[mutt]

ah shucks.... :O :O :O

Mutt.

[Bally Heck]

Missed approach climb gradients should be predicated on engine out performance for Perf A aircraft. (In the approach configuration) I think there is a JAA requirement for this to be greater than 2%.

However, as the aircraft will normally be at or below max landing weight when going around, which will typically be 10% or 20% below MTOW, the missed approach climb gradient should be somewhat better. Our ops manual for 757/767 give a minimum OEI climb gradient for missed approach of 5% at MLW.

If in doubt, use the higher minima!

[Old Smokey]

A very good point Bally Heck, it's good to see that some other operators also consider OEI gradients for 2 engined aircraft for missed approaches.

For the aircraft that I'm responsible for, the manufacturer's Approach Climb data was thrown out (the 2.1% stuff) and data for 2.5% substituted instead to at least meet the Gross Climb requirements for missed approach.

I sneaked it in as part of the submission for the AOC (I hope that the boss isn't reading this), so we can't go back on it now.

For all of the reasons that you stated, it is very rare indeed that this 'self imposed company limit' to have any impact on landing weights, except under the most extreme of circumstances.

Old Smokey

[wondering]

The little box with ground speed and rate of climb shows the climb gradient. Go to the 100kt column and devide the rate of climb by 100. The result will be the climb gradient. Or multiply the climb gradient by 100. That will give the rate of climb required when climbing with 100kt. Now adjust the rate of climb to your actual climb speed (ground speed)

[mutt]

'self imposed company limit'

Why do you consider it a self-imposed limit? The regulations call for 2.1%, however, the MAP requires at least 2.5%, if you intend to follow the MAP, then surely this 2.5% becomes a legal limit rather than a self imposed limit?

Bally Heck
which will typically be 10% or 20% below MTOW I presume that you are talking about the 757/767 in particular? What temperature are you talking about for the 5% at MLW?

Mutt.

[Bally Heck]

Mutt,

A 2.5% missed approach climb gradient is the standard for determining minima for an instrument approach. Most aircraft can do considerably better than this and those that can't will hopefully be all too aware of their aircrafts deficiency and higher minima will be imposed.

Some airfields have different minima for different missed approach climb gradients, Dalaman has ILS minima of 1210 feet for 2.5% gradient and 210 feet for 8%! Regretably with no intermediate values to allow lower minima for say 5% gradient.

The 5% gradient published for 757 and 767 at MLW is one size fits all. The aircraft will manage at least this figure at all temperatures with a crook donk.

[mutt]

The 5% gradient published for 757 and 767 at MLW is one size fits all. The aircraft will manage at least this figure at all temperatures with a crook donk.

Thanks for that, we operate the B777, for one particular airport with a 6% MAP gradient, we have a band of landing weights versus temperatures of over 40,000 kgs! Hence my interest in the single value for the 757/767.

Cheers.

Mutt.

[Old Smokey]

MUTT,

RE : "Self imposed company limit" - You're dead right of course, it IS a legal limit to achieve at least the mimimum MAP gradient. A bad choice of words on my part, both of the regulatory authorities that I answer to require that "Provision shall be made to ensure that the missed approach procedure employed shall be such as to ensure obstacle clearance with an engine inoperative during the missed approach" (Not the exact words, but a meld of the words of the 2 authorities). In both cases my predecessors nominated increase of the MDA to comply with the requirement. This was, in both cases, acceptable to the authority. I considered it very messy, the pilot does not have the facility to trigonometrically find the increase in MDA resultant fron Approach Gradient, 0.4% Delta between 2.1% and 2.5%, and Delta altitude between MDA and acceleration altitude.

Instead, as I mentioned, I discarded the 2.1% Approach Climb data, and inserted 2.5% data instead as the standard. For gradients >2.5%, tabular data is available for MLW in the environmental conditions to achieve the higher gradient.

The added bonus is that whereas very few pilots used the old 'increased MDA' method, I regularly see pilots now using the data as described.

"Nominated Technique" would have been a better choice of words than "Self Imposed".

Regards,

Smokey