Saturday, March 22, 2014

Fitting In

I'm working out of an airport where traffic has outstripped construction and the construction that is trying to catch up has made the taxiways and frequencies even more congested. When I get a word in edgewise with ground I'm cleared to taxi, but then have to pull over for a do-si-do at the compass rose so an opposite direction caravan can get by. Wait a few minutes stacked up behind traffic for departure, then cleared for the immediate, with a northbound turn as soon as able so they can keep pumping out faster traffic.


On the way home, I'm sequenced, allowed to descend towards the runway, and then told to keep it in close behind the departing jet. The controller's goal and hence mine is to put me on the pavement as soon as the jet is safely out of the way. I don't want to land into jet blast, the disturbance to the air made by the jet engines as the aircraft accelerates along the pavement, but I don't have to worry about his wake turbulence, because the vortices made by the wings of a flying aircraft don't start until rotation, and I will be stopped and turned off the runway before the point at which the jet gets airborne and the vortices start. I hear another aircraft behind being told to bring back the speed, follow the ... ATC gets my type wrong, but he's to be forgiven. I know it's me, and from the point of view of the B737 pilot behind me, we're much the same.

Someone on frequency asks the controller if they have software that advises them of traffic conflicts or just use their own cleverness. The controller assures them it's just cleverness and the next few calls to tower include praise for the controllers' cleverness. They have to undergo some pretty comprehensive aptitude tests for that job, and then a lot of training and supervised practice, so the cleverness is innate and trained.

I keep it close behind the jet, and plan to keep my speed up to the intersection where they usually ask me to exit. The fading jet blast affects the flare giving me a sudden headwind that dies, I bubble up and then touch down harder than I planned to before I can bring up the power to compensate. I've lost all my speed, because of that, but just as well because ATC asks me to exit on a sooner taxiway than I'd planned. I can refuse that if I consider it unsafe, but a bit of braking and I do it. The 737 must have landed behind me, and by the time I get my taxi clearance and turn onto the parallel taxiway there's a CRJ taking off.


majroj said...

Does jet exhaust pose more of an issue with very cold air, or warmer or hot air? Just curious.

Air (and field) traffic controllers are a breed unto themselves.

Ed Davies said...

“…and I will be stopped and turned off the runway before the point at which the jet gets airborne and the vortices start.”

You hope. What if you have to go around - e.g., if the jet blast had upset your landing a bit more? OK, you'd probably actually climb above the vortices but it does seem a bit dubious.

Anonymous said...

I like operatons like that. It shows (again) why human beings will never be replaced by computers.

@Ed ... vortices descend at about 500 fpm, and a slight heading change ensures lateral clearance.

Aviatrix said...

majroj: I don't have any experience or training that suggests the effects of jet blast differ with outside temperature. The blast is always pretty hot. In the winter they can blow snow onto you, or melt snow that can refreeze into ice. The blast doesn't linger, it's present behind the jet and attenuates quickly with distance.

Ed: The vortices won't start until the point the jet rotates which will be well down the runway. To be clear in cse ont everyone realizes: jet blast and wake turbulence vortices are different things.

kbq said...

Completely off topic, but the kind of cross winds 'Trix says she likes. :-)