View Full Version : Approach Climb

14th Feb 2002, 04:10
Could anyone please give me the history/reason why the min approach climb gradient(twin)required is 2.1% for an instrument appraoch down to cat 1 min (200 or above) and yet the PANS-OPS missed approach segment, climb gradient required/clearence is based on a 2.5% gradient.

Also, please correct me if I am wrong, is it not the operator's responsability to ensure that the a/c will achieve, at it's planned landing weight/forcast temp's, the 2.5% even though the min required 2.1% could be achieved?

Many thanks

14th Feb 2002, 08:33
The approach climb is a one engine inop certification requirement. It has nothing to do with missing obstacles.

The approach chart requirements are designed for use by all types of aircraft, not just 2 engine jet transports. It is simply a standard. Only you will know if you can meet it or not if you lose an engine.

14th Feb 2002, 11:31
The design standard WAT limits have been around since Pontius was a pilot ..... one would have to delve deeply into the depths of ICAO archives to find the original rationale for the various gradient requirements ... unless you just happen to know an 80 year old airworthiness engineer who just happened to work in that area as a boy ....

16th Feb 2002, 08:26
Thankyou Quid, I appricate that, but, and I have worded my post badly, I was really wondering which came first. Approach climb gradients or the min design gradient for the missed approach?

But as John said it all probably goes back a little too far!

While we are on the subject of the missed approach could anyone shed any light on where the min height for the level acceleration came from. The PANS-OPS document states this height to be 820ft, where did this figure come from? It seems like an odd number to me.

Best Rgds

16th Feb 2002, 09:31

Which ICAO doc are you using? My recollection of PANS Ops 86 is that there is no level acceleration segment included in the design. Unfortunately, I do not have one at hand to confirm that - maybe we have a procedure designer lurking somewhere (OzExpat?)

16th Feb 2002, 20:29
4dogs hi, it's an extract from ICAO DOC 8168.


16th Feb 2002, 21:42
Slick - is it 820 ft because it's a conversion from 250 metres perhaps?

17th Feb 2002, 05:44
It is VERY important, people, to remember that the WAT limits are minimum airworthiness design standard gradients and have nothing much to do with real operations, except in respect of determining relevant maximum gross weights.

The TERPS/PANS OPS considerations look at a raft of different concerns ... I would be wary of trying to correlate one with the other .. However, it is essential to keep in mind that one must not just mindlessly blast off at WAT limited weights and then be surprised when the aircraft hits a hill during the overshoot ....

17th Feb 2002, 08:38
When the 3rd Edition of Pans Ops first came out, back in 1986, there was provision for a level acceleration segment. It was subsequently removed, but had existed for so long that many procedures are still likely to state something along the lines of "climb to (altitude) prior to level acceleration".

It was a dreadful pain to have to build into a missed approach. Made the design length much longer, even for relatively short climbs. After building the initial missed approach segment at 2.5% to the level acceleration altitude which, in itself took a lot of fiddling when the terrain is difficult, then 6 miles of level flight, followed by subsequent climb (if necessary) to lowest holding altitude (or whatever) at 1%.

I'm glad we don't have to go thru all that malarky any more!