Owen,
Thanks for flying through and for your question. Many here have already done a great job of answering your question. I wasn't there, so I cant answer specifically to why the controller on position gave the instruction. What I can say is that this is a normal instruction for Atlanta arrivals. Typically, we do not issue the descent that far out as you are describing. However, it's important to remember that we will issue altitude instructions for several different reasons, some of which may or may not be obvious to the pilot. It could be traffic, an agreement between adjacent sectors or facilities, or airspace. In general, we like to allow the pilots to fly the speeds, altitudes, and routings that they file -- we understand those things are chosen for a reason. Although our primary responsibility is separating traffic, we also have to provide for the safe, orderly, and expeditious flow of it. You may occasionally receive a more or less economic altitude, a more or less desirable routing or speed to achieve those goals.
Others have already touched on this, but many times we will issue "pilot-discretion" descents. We experience many pilots who fly through the airspace and misunderstand this clearance. I can't be certain, but it is definitely possible this was the cause of a misunderstanding in your case. It's important to recognize the difference between receiving a "PD" descent and a hard altitude. If given a pilot-discretion descent, the controller will use the phrase "...descend at pilot discretion..." followed by an altitude to maintain. In such a case, the pilot need not start the descent immediately. You may begin your descent, as the clearance implies, at your discretion. If a controller gives you a hard altitude, they will use the phrase "...descend and maintain..." followed by an altitude. If given this clearance, the pilot should start a descent promptly to the assigned altitude. We expect jets to descend at a rate of at least 1,000 feet per minute when we instruct an aircraft to "climb/descend and maintain...".
As someone already suggested, its a good idea to take on a little bit of extra gas to protect against any unforseen delays, such as being descended early, vectoring, reroutes, holding, etc. You as the pilot have to make the determination of what you're comfortable with as far as the fuel goes, but I will say it is perfectly okay to burn into your reserve fuel -- you just cant plan to use it when pre-flight fuel planning (it has to be in addition to the fuel required to fly from A-B and from B to your furthest alternate).
I cant say whether or not the controller made a judgement error or whether the early descent as you described it was necessary, but I will say you did the correct thing by advising the controller that the descent would put you in an uncomfortable fuel situation. We can almost always coordinate and get you what you need when it comes to those types of scenarios.
Please feel free to send me an e-mail directly if you have any other questions and I will be happy to respond via e-mail or meet with you on our Teamspeak to discuss them.
Best Regards,
Cardin Pelletier
vZME Training Admin
TA@vzmeartcc.com
