SKYW Pilot said:
When's the earliest you can turn after departure in IMC. Say you're doing a 600 600 600 RVR takeoff and the DP requires a left turn to a heading. I've always heard 400 feet, but never been able to find it in the FAR's/AIM. Does the rule differ for IMC/VMC? Part 121/91? I fly for a 121 carrier and we don't have anything specified in our SOP when to turn, so I'm looking for the "Fed" answer. If anybody knows where to find it, can you post the reference? Thanks in advance!
I don't think it is written anywhere. I've looked, and asked and never come up with anything in any regulation which would tell you that. You can, however find the basis for the 400 ft in the TERPS, in Chapter 12 which covers desiging departure procedures. They provide for Diverse departures, straight departures and turning departures. Straight departures, don't involove a significant turn (less tha 15 degrees) so aren't relevant. The Diverse departures allow a turn in any direction after takeoff, (ie: no specified Obstacle DP) and turning departures are the ones which specify: "left/right turn to heading XXX (more then 15 degrees form runway heading) "
For both the Diverse and Turning departures the Obstacle Identification Surfaces (OIS) begin with a straight segment of 2 nm, sloping to 400 ft above the departure end of the runway (DER) THe remainder of the OIS begins at 400 ft above DER, so once you're more than 400 ft above the DER, you are above the rest of the OIS. The specifications for a turning departure go as far as to specifically defne a turning departure as one which involves a climb on runway heading to 400 feet than a turn to a heading. A turn immediately after breaking ground to a heading 90 degrees from the runway heading could concievably put you below the OIS, and below obstacle protction, but that would require a pretty agressive turn.
So, we haven't answered the question really. Are you required to climb to 400 ft before turning? Well, in IMC it's a pretty good idea, regardless of the legality. Besides the question of an early low turn taking you outside of obstacle protection, there's a lot to be said for not doing anything but fly straight while you're close to the ground, reconfiguring the aircraft and transitioning from being on the with visual references to being in the air with out.
For Part 91, I would say no, there is no requirement to follow a departure procedure under Part 91, so observing the climb to 400 ft is not required. Under part 121 and 135 you are required to follow departure procedures, so presumably, you would be required to climb to 400 ft before turning. That is the way departures are designed, however, it's almost impossible to know that without reading the TERPS.
One thing to consider, some departures are worded in a way that suggests the turn needs to happen pretty quickly. It's not uncommon to see "left turn as soon as soon as practical" and I know a couple of places where its: "
immediate left turn" I would say that in these cases, it's ok to start the turn as soon as you can.
Does all this translate to a requirement to not turn before 400 ft in good visual conditions? That's less clear. Let's just put it this way, On a 121 flight with a fed on the jumpseat, I would be careful to make no turns below 400 ft in any conditions. If you do, you know you're on solid ground.
