[ QUOTE ]
Oh boy, here we go with a long answer. Hold on tight.
A heavy is determined by weight, as mentioned before. This puts the aircraft into a category. There are several different scenarios that a controller will keep aircraft separated by minima standards. These are Same Runway Separation (landing and departing), parallel runway separation, visual approach separation, and radar approach separation. Just to note a B757 is always considered a heavy because of its design. Another interesting note is that the 767’s used to be heavies and now they are in the Large category.
Same Runway Separation (SRS)
1. When only Category I aircraft are involved- 3,000 feet.
2. When a Category I aircraft is trailing a Category II aircraft- 3,000 feet.
3. When the second aircraft or both are Category II aircraft- 4,500 feet.
4. When either is a category III aircraft- 6,000 feet.
If this separation doesn't exist by the time the arriving aircraft crosses the landing threshold, the controller must issue a go-around. It is not the pilot’s responsibility to decide if there is enough separation.
However, if radar separation is being applied, only the following minimum separation must exist before the trailing aircraft is airborne.
1. A heavy behind a heavy- 4 miles.
2. A large/heavy aircraft behind a B757- 4 miles.
3. A small behind a B757- 5 miles.
4. A small/large behind a heavy- 5 miles.
If an aircraft is taking off behind a heavy/B757 on the same runway that has a displaced landing threshold and the projected flight paths will cross, the separation must be two minutes. The reduced radar separation doesn't apply in this case. Also, ATC shall not approve pilots’ requests to deviate from the required wake turbulence separation if the preceding aircraft is a heavy/B757.
Terminal Procedures (this gets detailed)
- For an aircraft that is less than 40 miles from the antenna that provides a facility with their radar information, 3 miles separation is provided.
- For an aircraft that is 40 miles or more from the facility radar antenna, 5 miles separation will be used.
However, it must be noted that greater separation may need to be provided if wake turbulence is involved. Wake turbulence separation minima are as follows:
1) 4 miles for a heavy operating behind a heavy.
2) 5 miles for a small or large behind a heavy.
3) 4 miles for a large or heavy behind a B757.
4) 5 miles for a small behind a B757.
Now for the exceptions. (Come on, you had to know there would be exceptions.)
Aircraft operating in the terminal area will be provided the same separation as in the en route environment, with a few minor adjustments. They are:
1) 4 miles for a small behind a large.
2) 5 miles for a small behind a B757.
3) 6 miles for a small behind a heavy.
This separation must exist when the preceding aircraft crosses the landing threshold. For example, you are vectored to the final approach course in your C172 and are 5 miles in trail of a heavy aircraft. This is legal, but your speed must be such that during the approach the separation increases to the required 6 miles by the time the heavy aircraft crosses the landing threshold.
This information was copied from a UVSC lecture, without permission.
[/ QUOTE ]
In the AF, we've also got RRS or Reduced Runway Separation. 3000' between similiar aircraft, 6000' between disimiliar. That means that F-16s on landing need only be 3000' apart, so on a 12,500' runway, you can have 3 aircraft rolling out with another touching down so long as the rollouts are on the "cold" side of the runway.
MD