Airline Pilot Forums

All.

I got into this discussion with someone the other day so I thought I would post this. I am sure most people know about this with regard to airports like aspen and getting out of there IFR but for along time i wasn't one of them. This is regarding what is required for takeoff performance IFR

AC 120-91 Airport Obstacle Analysis (http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgAdvisoryCircular.nsf/0/55A6248632ED6E8D86257184005A2188?OpenDocument)

I've yet to hear a FSI instructor teaching performance say "ODPs are predicated on all-engines operating takeoff performance". Which is pretty disappointing, because they are - and this seems to be one of the most misunderstood things in aviation.

Every time I have to do a performance problem by extrapolating second-segment OEI climb gradients to the top of the LINDZ, I shake my head.

You may be in class with 135 crews or maybe the instructors are misunderstanding the requirements. At the end of the day though, legal isn't always 'safe'. What would you do if you torched an engine without the required climb gradient? Like anything else it comes down to risk management I guess.

You may be in class with 135 crews or maybe the instructors are misunderstanding the requirements.

No to the former...and I'm afraid yes to the latter.

The only instructor I've ever had that acknowledged the true nature of ODP performance was a former CitationShares pilot. A breath of fresh air to see someone employed by a 142 training center not perpetuate one of the largest performance misunderstandings in business aviation.

At the end of the day though, legal isn't always 'safe'.

I agree 100%...but extrapolating second-segment climb performance to the top of an ODP ain't exactly an accurate representation of actual aircraft performance, and isn't required per the procedure.

Every time an instructor says "You HAVE to do this to ensure performance", the response should be "No, actually, I don't."

It really shouldn't be that difficult to acknowledge the requirement of an ODP, but also emphasize the importance of ensuring climb performance/obstacle avoidance via some means (reducing weight to meet gradient, runway analysis special procedure, etc).

Like anything else it comes down to risk management I guess.

Indeed...

You may be in class with 135 crews or maybe the instructors are misunderstanding the requirements. At the end of the day though, legal isn't always 'safe'. What would you do if you torched an engine without the required climb gradient? Like anything else it comes down to risk management I guess.
I believe nowcorporates sentiment is that it is illegal 121/135 or unwise (91) to depart any airport with out meeting the minimum required climb gradient for OEI. Using the AFM to determine you climb gradient is pointless. The best way to accomplish this is to use Airport Analysis (APG) and reduce weight as applicable via the climb limit weight read from the chart. If your weight is at or below the charts required Climb limit weight, you will meet the OEI ODP requirements and thus be using the most conservative weight.
It does seem that people get wrapped around the axle with this concept. It is simple, Use APG or whatever company to find your max allowable weight for takeoff. If you bag an engine on TO use the OEI DP to clear obstacles if prescribed. If both engines work then use the JEPPESEN DP if prescribed, otherwise its climb on course. If its VFR and you are on an IFR flight plan but dont want to use the DP then tell ATC you want a VFR climb on course. This is all you need to know for daily operations. Unless you are in the right seat. Then you must remember to take the fat girl during wingman operations.

I believe nowcorporates sentiment is......


Nah, my sentiment is that those who can analyze a performance class or problem to a knats a$$ or spew certification requirements USUALLY lack experience and/or common sense. I can take what is discovered (and usually 90% of the time WRONG) from one of these exercises and give the real answer in about 4 mins using a flightplan and APG data.

At the end of the day the boss just wants to know if he can come or go and where we are going if not. Not rocket science....but remember we are dealing with pilots - they like to try and impress each other with this "knowledge" of charts, lines and regulations....even worse when they wind up teaching this crap.

With the resources available today its amazing we still sit through this exercise at FSI/CAE recurrents.

At the end of the day lets also keep in mind, legal is not always smart. A smart pilot can convince Mr Rich there is a long term, best way of doing things, and that usually does not involve graph analyzing.

Ovrtake92

And if you used the Climb Lim column and the runway was obstacle limited, you'd be wrong. The weight to use in the obstacle case would be the one with xxxxx-O, signifying Obstacle. The Climb Lim column is OEI climb certification limit, for twins 2.5%, for quads, 3.0% and something in between for tri-motors.

GF

right...use the most limiting weight on the chart for your temp

I believe nowcorporates sentiment is that it is illegal 121/135 or unwise (91) to depart any airport with out meeting the minimum required climb gradient for OEI. Using the AFM to determine you climb gradient is pointless. The best way to accomplish this is to use Airport Analysis (APG) and reduce weight as applicable via the climb limit weight read from the chart. If your weight is at or below the charts required Climb limit weight, you will meet the OEI ODP requirements and thus be using the most conservative weight.
It does seem that people get wrapped around the axle with this concept. It is simple, Use APG or whatever company to find your max allowable weight for takeoff. If you bag an engine on TO use the OEI DP to clear obstacles if prescribed. If both engines work then use the JEPPESEN DP if prescribed, otherwise its climb on course. If its VFR and you are on an IFR flight plan but dont want to use the DP then tell ATC you want a VFR climb on course. This is all you need to know for daily operations. Unless you are in the right seat. Then you must remember to take the fat girl during wingman operations.

good post...last sentence being most important.. after all they need love to