Procedure Design Gradient (PDG)

28.10.2004

Submission:

As you know JARs, et al certify twin engine a/c to fly on one engine on a go around with a demonstrated performance capability of 2.1% "Approach Climb" gross path. YET (and thanks to your site's topics which has cleared some of my problems) that Jeppesen's OCH performance criteria is predicated on 2.5% gross path AND that most pilots miss the dangerous point that Hong Kong on some of its approaches allows a/c to fly down to 222 odd feet Decision Altitude on an instrument approach BASED on 5.1% (if I remember correctly) with a little added "note" saying its for 5.1% climb gradient YET over the page it has a FAR HIGHER minima for 2.5% climb gradient BUT if a two engine a/c has an engine failure and needs to go around at the 2.5% nominated height then surely it cannot meet this requirement at max landing weight if the a/c's performance is "approved for 2.1% Approach Climb". So the bottom line is that airport minima's with anything higher than 2.1% gross climb path is a problem for twin engine jet aircraft? Because Hong Kong is a classic, off runway 25 one turns right and back towards high ground (I wonder why the approach was so designed) and if one overshoots to carry out that procedure and is heavy and on one engine the a/c will never clear the mountains if the 2.1% gradient minima is adhered to. This anomaly could be deadly!

Mike Dixon - A320 Captain - Vietnam Airlines

Answer or Commentary:

(I.W.

You seem to be right that it looks like an anomaly between what is designed and what is certified (2.5% and 2.1%). Let me once again say that the ICAO Pans-Ops procedure design criteria do not take into account the situation of an engine out.

Well over 50% of all the minimums (OCA/H) on approaches are dictated by missed approach obstacles. If a 2.1% not 2.5% missed approach climb gradient was an ICAO requirement then a lot more approaches would be penalised by missed approach obstacles and a lot of approach minimums would have to be increased. As I see it a 1 engine out is an emergency situation and as the pilot in command you can basically do what ever you consider appropriate to ensure the safety of your aircraft. Most airlines develop their own 1 engine out procedures for each airport they fly into (criteria laid down in JAR-Ops). Airline company 1 engine out procedure developers usually try to design a 1 engine out procedure that follows the official procedure but if that is not possible other procedures are developed. I have seen cases where the missed approach or a SID turns right whereas the 1 engine out procedure turns left. Do any of the other pilots or procedure designer out there have comments?)