Minimum Rate of Descent

[lonelyoutpost]

As an aviation enthusiast, I've been pondering the following question for a while now and wonder if anyone could enlighten me.

If a plane is asked to descend by ATC much earlier than planned (say 100nm), is the pilot required to descend at a minimum rate (like 1000 fpm)? For the sake of fuel economy I can see that an airline would want a plane to stay at the most efficient flight level for as long as possible, but ATC, of course, has its own agenda, primarily safety and logistics. So there must be some legal minimum rate. If any real world pilot can enlighten me I'd be very grateful.

Thanks,

Matt

[kcockayne]

As a retired ATCO, I am not aware of any regulation governing this situation. If the pilot has any doubt about this, all he has to do is ask. Otherwise, if I had instructed an aircraft to descend earlier than usual, I would expect the pilot to do so at a rate to suit himself; or for me to stipulate a required rate of descent - especially if this were for separation purposes. Actually, I cannot envisage any reason for ATC to issue such an instruction, other than for separation, or to comply with letters of agreement with other units. If this is critical, ATC would instruct a descent rate.

[Equivocal]

3.2.2.3 Maximum Rates of Climb and Descent
3.2.2.3.1 In order to ensure the credible interaction of Airborne Collision Avoidance Systems and ground based safety nets, other than aircraft in emergency and certain specific conditions for military aircraft (as detailed in Military AIP and MAA Regulatory Publication RA 3000 Series), all aircraft when operating under normal circumstances, when inside Controlled Airspace within the London and Scottish FIRs/UIRs should not operate with a climb or descent rate exceeding 8000 FT per minute. Aircraft when first approaching a cleared flight level and/or when changing flight level in Controlled Airspace should ensure that the vertical closure speed is not excessive. It is considered that, with about 1500 FT to go to a cleared level, vertical speed should be reduced to a maximum of 1500 FT per minute and ideally to between 1000 FT per minute and 500 FT per minute. Pilots should ensure that the aircraft neither undershoots nor overshoots the cleared level by more than 150 FT, manually overriding if necessary.
3.2.2.4 Minimum Rates of Climb and Descent
3.2.2.4.1 In order to ensure that controllers can accurately predict flight profiles to maintain standard vertical separation between aircraft, pilots of aircraft commencing a climb or descent in accordance with an ATC Clearance should inform the controller if they anticipate that their rate of climb or descent during the level change will be less than 500 FT per minute, or if at any time during such a climb or descent their vertical speed is, in fact, less than 500 FT per minute.
3.2.2.4.2 This requirement applies to both the en-route phase of flight and to terminal holding above Transition Altitude.Note: This is not a prohibition on the use of rates of climb or descent of less than 500 FT per minute where necessary to comply with other operating requirements.

Can't remember how much of this comes from international standards and how much is UK specific, but it is an example and you might find similar statements in other States' AIPs.

[lonelyoutpost]

Thanks both for taking the time to respond. That's really interesting.

Matt

[Speed_Alive_V1]

Yup 500ft/min is the minimum expected in climb/descent. If you can't do that flight crew should advise us, but we are constantly watching your rate ourselves anyways.
If it's a slow descent, and we need you under traffic we'll tell you about the traffic and ask for a specifc rate of descent to ensure seperation. For slow climbs, normally we wouldn't give you a clearance to a level above any traffic anyway, so that there is always positive seperation in place. Often for slow climbers leaving our FIR, we will call up the next controller and ask if they will take them in the climb.

For level capped waypoints, often I will say "When ready, descend FL330, cross waypoint xxx level". If there was traffic in the way, it would be a case of a vector to ensure lateral seperation, an initial descent, then when clear of the traffic, own nav back to the point and then the when ready clearance.

Cheers

[lonelyoutpost]

Thanks. That makes a lot of sense. Very interesting.

Cheers,

Matt