How to comply with restrictions?

[asdf12321 0]

Hi guys. I have a newb question that has bothering me since I started using RC:What's the expected descent rate, in RL? I ask because I can rarely comply with instructions like "... I need you level on 30 miles or less", or "cross 20 miles from xxx at yyy...". I have a short time to descend several thousand feet and don't know how to do it other than plummeting down.

[jd 57]

Hi guys. I have a newb question that has bothering me since I started using RC:What's the expected descent rate, in RL? I ask because I can rarely comply with instructions like "... I need you level on 30 miles or less", or "cross 20 miles from xxx at yyy...". I have a short time to descend several thousand feet and don't know how to do it other than plummeting down.

the crossing restriction is given 30 miles from where you are crossing. the initial descent clearance from cruise is give long before then, in plenty of time to make the eventual crossing restriction without too much distress.are you starting down from cruise, when requested?what altitude are you at when you are given the crossing restriction? what is the crossing restriction altitude?jd

[asdf12321 0]

OK first and foremost keep in mind I'm a newb so tell me if I'm doing something wrong. Obviously the answer to your questions would vary from flight to flight, but let me use my most recent flight as an example: I was cleared down from my crz lvl to fl240, then to 18000, then to 15000 and was told to do so "when ready". I kept descending without stop and when at about 15000 was told to descend to 11000 in 30 miles or less. I couldn't make it, and was told so by the controller.

[airliner_75 0]

OK first and foremost keep in mind I'm a newb so tell me if I'm doing something wrong. Obviously the answer to your questions would vary from flight to flight, but let me use my most recent flight as an example: I was cleared down from my crz lvl to fl240, then to 18000, then to 15000 and was told to do so "when ready". I kept descending without stop and when at about 15000 was told to descend to 11000 in 30 miles or less. I couldn't make it, and was told so by the controller.

Do you mean that descending from 15000 to 11000 feet with a distance of 30nm is impossible?How fast are you flying?As I understand it you descend from 15' feet to 11', or am I wrong? 30nm to descend 4000 feet is very very long time.

[asdf12321 0]

OK that sound logical: either I'm going too fast or not descending fast enough. Which bring back my question: what should my descent rate be? And since we are on that, should I have lowered my speed before starting my descent, or waiting to reduce to 250 at 10000ft is reasonable?

[Randh 0]

OK that sound logical: either I'm going too fast or not descending fast enough. Which bring back my question: what should my descent rate be? And since we are on that, should I have lowered my speed before starting my descent, or waiting to reduce to 250 at 10000ft is reasonable?

For a jet airliner, the descent rate varies between 1,500fpm and 4,000fpm. Pilots with discretion at 36,000ish feet usually start their descent about 100nm from the airport. At this point the descent rate is usually a uniform 3,000fpm, although it varies with speed restrictions, and what ATC tells you. (Sometimes in RC they'll ask you to expedite through a flight level, which means you need to raise your spoilers and dive).I use payware addons like the Wilco Airbus collection, ERJ's, and Captain Sim 757 and 767, and they all have an FMS which calculates the optimal descent rate, which generally speaking is the descent rate at which the airplane reaches its destination on idle thrust. Obviously due to crossing restrictions and the like, it's impossible to maintain this optimal descent rate, but I have never busted an altitude restriction by relying on the FMS to descend me to 11-12,000 and have comfortably approached and landed at the airport afterwards.

[asdf12321 0]

Got it. Thanks a lot. I learnt a lot from your post.

[ronzie 21]

If you have an FMC I suggest putting a destination fix range ring about 40 nm out. This will display on your navigation display and give you an estimate of where your crossing restriction will appear on your flight path. You can then adjust your descent airspeed and vertical descent rate (V/S) to comply. I prefer to balance these so an idle descent thrust is used as much as possible matching many real world conditions. The AP will adjust aircraft pitch so you don't reach the restriction too early where you'll need to cruise in level flight for an extended time wasting fuel.

[VIPERGTSR01 22]

With the PMDG MD-11 (which I am flying the most) you can't set fix range rings (MD-11 design isssue) but what I most commonly do is when asked to descend by RC4.3 I start off about -2100 to -2200 fpm which the aircraft can easily maintain without speedbrake required, after I get below FL200 I usually knock it back to -1800 or so as it becomes harder to maintain speed (FMS descent speed of around 300IAS) without using speedbrakes which I rather not do. I may adjust the VS slightly up and down watching the distance I have left to the 30nm crossing but I never have issues getting down to requested crossing restriction this way with no speedbrake. Although slowing the aircraft down from ~300IAS to 245 before 10000ft sometimes requires some speedbrake to make it happen quicker. Generally allowing the FMS to do this alone sometimes can annoy the ATC as the aircraft likes to keep it's speed up and only drop it at the last minute by pretty much fully leveling off until 245 is reached, depending on weight/winds etc it sometimes even crosses above 250 so I like to give it a hand or start the slowing eariler with manual speed input.

[chrispeel 0]

You can always take back the comms from Otto before descent.Then you will be able to tell ATC you want to have a PD descent(Option 3) and later that you will be unable to make the crossing altitude/flight level at the 40 mile mark.(Option 6)This is useful if you're landing the wrong way round.E.G.If LAX is on easterlies and you are coming in from the east.Many people have written in to this forum to say that 11000 feet is too high if making a straight in approach to a sea level airfield in a heavy.It can be tight and as I understand it may well be changed in RC5.As Ray has advised many times the best plan is to get to minimum clean speed or thereabouts by that point.

[Cras 6]

The absolute best way to deal with RCs crossing restrictions is to have good situational awareness in your plane. Know where you are, how fast you are going (wind corrected), what your route is, and what runway you will most likely be assigned. Then, when you are given a clearance to descend that doesn't jive, you can ask for PD, or when you are approaching a point where you think you should being your descent but have yet to receive clearance (doesn't happen very often with RC, but I have had it happen), you ask for clearance preemptively. And be truthful. If the 11,000 or 12,000 altitude restriction doesn't make any sense to the arrival you are flying and the approach you are expecting, say you are unable. Remember, as the Pilot In Command, you first responsibility in all cases is to fly the plane safely and responsibly. If ATC (be it RC or VATSIM et al) tells you something that would require you to fly otherwise to comply, tell them so, and await for plan "B".