Space between departures

[Speed]

I know landing spacing has been discussed here before, but what about departures? This morning Denver was launching traffic so fast, they were clearing airplanes to take off before the prior one reached rotation. What are the separation requirements here? We were discussing (hypothetically) how you would explain to the company that we had aborted a takeoff because the aircraft in front of us on the runway had aborted their takeoff... wouldn't look real good.

 

[poadeleted20]

3-9-6. SAME RUNWAY SEPARATION​

Separate a departing aircraft from a preceding departing or arriving aircraft using the same runway by ensuring that it does not begin takeoff roll until:

a. The other aircraft has departed and crossed the runway end or turned to avert any conflict. If you can determine distances by reference to suitable landmarks, the other aircraft needs only be airborne if the following minimum distance exists between aircraft: (See FIG 3-9-1 and FIG 3-9-2.)​

​

1. When only Category I aircraft are involved- 3,000 feet.

2. When a Category I aircraft is preceded by a Category II aircraft- 3,000 feet.

3. When either the succeeding or both are Category II aircraft-
4,500 feet.

4. When either is a Category III aircraft- 6,000 feet.

5. When the succeeding aircraft is a helicopter, visual separation may be applied in lieu of using distance minima.

​

NOTE-

Aircraft same runway separation (SRS) categories are specified in
Appendices A, B, and C and based upon the following definitions:

CATEGORY I- small aircraft weighing 12,500 lbs. or less, with a single propeller driven engine, and all helicopters.

CATEGORY II- small aircraft weighing 12,500 lbs. or less, with propeller driven twin-engines.

CATEGORY III- all other aircraft.

​

​

There's more, but this is pretty much the answer to your question. Source is the ATC Handbook, http://www.faa.gov/ATpubs/ATC/

 

[Flyboy]

You can choose to wave the departure spacing as long as the traffic isn't a heavy. (defined by max weight but I dont know the figure. THink 747, 757 etc...)

Is it a good idea? It depends. Out of a class B you might sit for a long time during busy times. I do it regularly out of Charlotte, but only when I'm sure I can be airborn way ahead of the departing aircrafts rotating point.

 

[Skip Miller]

Out of a class B you might sit for a long time during busy times. I do it regularly out of Charlotte, but only when I'm sure I can be airborn way ahead of the departing aircrafts rotating point.

Yes, but you cannot outclimb the jets once they lift off. When following close behind a bizjet or 121 carrier, I routinely ask for a sidestep to the upwind side (a hundred yards will do it) or an early turn for wake turbulence avoidance.

-Skip

 

[poadeleted20]

You can choose to wave the departure spacing as long as the traffic isn't a heavy. (defined by max weight but I dont know the figure. THink 747, 757 etc...)

Flyboy is thinking of the wake turbulence wait, which you can waive, but only for a full-length takeoff (not for intersection takeoffs). Controllers are not permitted to waive the minimum separations listed above. Only way to takeoff closer together is to be in a formation.

 

[mdreger]

This morning Denver was launching traffic so fast, they were clearing airplanes to take off before the prior one reached rotation.

Where was the first departure, when the second started his departure roll? It takes quite some time for those engines to spool up, get all that mass moving, then lumber into position and line up on the centerline. I would guess they weren't trying that with a prop, or even a light bizjet.

 

[Flyboy]

Flyboy is thinking of the wake turbulence wait, which you can waive, but only for a full-length takeoff (not for intersection takeoffs). Controllers are not permitted to waive the minimum separations listed above. Only way to takeoff closer together is to be in a formation.

Ooops, you're right. (again)

Most departing GA traffic is given a turn right or left of the runway (usually heading 110 on the east side) immediately after takeoff so I guess that could be used for spacing. I have even been asked for "an early turn" meaning make the turn as quick as you can after lift off. And I imagine with the speed of most turbojets it doesn't take long to get the 3 minute spacing when they depart.

 

[poadeleted20]

Most departing GA traffic is given a turn right or left of the runway (usually heading 110 on the east side) immediately after takeoff so I guess that could be used for spacing.

As folks can see from the above-quoted portion of the ATC Handbook, that's correct:

"...by ensuring that it does not begin takeoff roll until ... [t]he other aircraft has departed and ... turned to avert any conflict."

I have even been asked for "an early turn" meaning make the turn as quick as you can after lift off.

That's a common request which I usually do my best to fulfill, but while most all of us are eager to please, we should not let such a request push us into doing something silly at low altitude/airspeed.

 

[Skip Miller]

And I imagine with the speed of most turbojets it doesn't take long to get the 3 minute spacing when they depart.

Nope, it still takes about 3 minutes.

-Skip

 

[Flyboy]

Nope, it still takes about 3 minutes.

-Skip

Does not...