Adherence To Clearance (Climbs Descents)
 

I need some help from the smart people in the room.

I recently had a friendly disagreement with a fellow pilot on the minimum climb rate and descent rate while on an IFR flight plan.

From my military training, we were taught 500FPM was the minimum climb or decent rate one could fly while on an IFR flight plan. If you could not meet these minimums, you were to contact ATC.

According to the AIM 2016 4-4-10 Adherence to Clearance d.
-When ATC has not used the term "AT PILOT'S DISCRETION" nor imposed any climb or descent restrictions, pilots should initiate climb or descent promptly on acknowledgement of the clearance. Descend or climb at an optimum rate consistent with the operating characteristics of the aircraft to 1,000 feet above or below the assigned altitude, and then attempt to descend or climb at a rate between 500 and 1,500 FPM until the assigned altitude is reached. If at anytime the pilot is unable to climb or descend at a rate of at least 500 feet a minute, advise ATC.

I can not find the term "optimum" defined in the Pilot Controller Glossary nor the AIM. Anyone want to venture a guess what optimum means? Optimum for me, the pilot? Optimum for the airplane? Optimum for ATC?

Second question, does anyone know any reference to minimum climb and descent rates in ICAO / PANS OPS?

Thanks for the help...

I cant speak to the ATC side, although you might find some info in their guidance handbook- FAA JO 7110.65W. The best answer from a pilot perspective is, it depends on the situation. Unless otherwise specified, TERPS is predicated on a minimum climb gradient of 200ft/nm for obstacle avoidance. Yes, there is also the requirement to advise ATC when climb rate is less than 500fpm. Rarely is this an issue unless at or near the max altitude capability of the jet. Most FMS software are predicated on climb at a specific airspeed and thrust setting, thus the actual climb rate varies. Also Most FMS software are "buffered" for smooth level- offs in that the last 500-1000ft are at reduced climb rate (mainly for pax comfort). The Airbus FMS always tries to achieve a 1"g" ride and will put pax comfort first over trying to meet a climb/descent restriction. "Managed" mode in the Airbus can get pilots in trouble if they don't understand how it works. I probably have not fully answered your question, but I Hope this helps a little bit at least..

You must be flying the 320. The 330 heavy is a pig and often falls below 500FPM climb rate before reaching level off. Big wing with little engines!

I just stick with the dictionary definition of optimum:

"Most conducive to a favorable outcome; best."

When I have a nice tailwind, then that means my optimum descent rate is 500 fpm since it keeps my groundspeed up and the fuel flow down.

Climb at least 500fpm, or advise ATC.

Descend at least 1500fpm on an unrestricted decent of more than 1000ft. If you don't maintain at least that you could mess up the controllers planning and create a conflict.

Doesn't apply if you have crossing restrictions, as long as you make them.

Weird, the default descent rate for the 737 in VNAV is only 1000FPM until it captures the path and goes to idle. ATC never says a word.

Is the 1500fpm descent in the AIM or something? I always descend 1000fpm if I haven't reached TOD. Never heard a word from ATC.

Did a little more digging. 8260.3 TERPS procedure design is predicated on appx 318 ft/nm standard descent. I am unable to locate any reference to minimum 1500fpm descent rate. Whatever it takes to make the crossing restriction...

Where is that written?

3 degrees flight-idle this is the best rule of thumb this is the formula GS say 500 kt cut in half ..so.. 250 add a zero so 2500 feet per minute. GET er Done hillbilly math.

Alt to lose x 3 = miles to BOD (no wind)

I've done a lot of my IFR flying in a C150 so I have some experience in not meeting 500fpm climb. ATC does ask you if you stopped climbing if you only get 300fpm or so. I just read back any altitude change "climb and maintain 5000, maximum climb rate 300fpm". Never been a problem.

perfInit,

Don't confuse TERPS (approach and departure design) with ATC enroute rates. There are minimum climb graidients for Victor airways, tho. I think it's 150'/nm below 6,000' MSL, 120'/nm between 6,000' and 10,000' and 100'/nm up to .17,999'.

AIM 4-4-10,

GF

Yup...if atc needs a good rate down they usually say so in the clearance. Otherwise if I am below path it's 1000 fpm...and never hear a peep about it. Rick is ill informed...

I notice that nearly seven months have passed, and despite several posts questioning the veracity of the claim, Rick has yet to respond to your question.


The answer is, it's not. At least, it's not written in anything authored by the FAA. If specific guidance WERE written, we would have a reference and a clear answer.

Instead we're left to debate the meaning of optimum. Until the FAA comes up with a definition, I will determine what's optimum for me in the particular situation when I receive such a clearance. If the controller needs something more specific for traffic clearance or LOA compliance or whatever other reason, I'll gladly comply with his specific instructions.

My FMS defaults to 750 feet per minute if I begin the descent early. Works for Honeywell, works for me. Works good, lasts long time.






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