Monday, August 21, 2006

Lots of Hot Air

On more than one occasion, I sat in a Caravan, just clear of the taxiway, waiting for a large jet aircraft to move because it was too close for me safely taxi behind it. How did I know this? Because I once carelessly taxied behind an MD11 that was just sitting there with its engines running. In my defense, I was tired, it was night, it was raining, the freight ramp was just ahead of me, and I was only thinking of getting some sleep. Lucky for me, the engines on the MD11 were at low idle and I just got buffeted around. I made a note to self: Don't do that again! Some of the other company pilots and I ended up discussing the situation the next day.

I was never taught how closely to taxi a Caravan behind a jet when following it to the runway for takeoff. I learned through careful and very conservative experimentation. The rule of thumb I came up with was that a minimum safe following distance for a heavily loaded (greater than 8000 lbs) Caravan was at least one wing span's length behind a jet aircraft. And I mean the wing span of the aircraft being followed, not a Caravan's wing span. If I was lightly loaded, I'd stay at least one and one half wing spans behind. And I'd stay even further back if the jet in front came to a stop and then needed to apply break-away power, which can really rock your world.

Taxiing behind some types of jets was more problematic than others. Following a B737, A320, B757, or B767 was not as bad because the wing-mounted engines were far apart, hence the jet blast was more spread out. I discovered I needed more following distance behind tri-engine jets because the jet blast was concentrated right on the taxiway centerline. I found the B727 was the worst in this regard.

Propeller aircraft can also create quite a stir. Many pilots, oblivious to this fact, simply push the throttle in without considering what might be located behind them. I've seen some biz-jet drivers do this when taxiing out from a GA ramp, too. Since it can be very difficult to see behind you in most aircraft, here are a few suggestions for courteous operation. You may have guidelines of your own, too.

Look behind the aircraft during preflight. If there are other aircraft parked behind you or there are hangars with open doors, consider repositioning the aircraft by hand (if practical) before beginning the engine start procedures.

Before starting engine(s), clear the area again. If it's practical to do so, yell "Clear!" out the window.

When ready to taxi, apply power in a smooth and gradual manner. This is especially important if there is debris or loose dirt around the ramp.

If you need to use a run-up area prior to takeoff, think about where other aircraft will taxi by. Especially consider where larger jet aircraft might turn or maneuver and try to visualize the best place to be so that you are far enough away to be unaffected by their jet blast.

Avoid taxing behind large aircraft that appear to be ready to start their engines. At many airports, the presence of ramp personnel standing in front of an aircraft, preparing to marshal the aircraft out of the parking spot, can be a good indicator of what is about to happen.

If ATC asks you to move closer than you are comfortable with toward a big aircraft, don't hesitate to say "unable."

When possible, tie your aircraft down when you're going to leave it unattended. A while back, I did a cross country flight with a pilot to a rural airport. When we arrived, I began attaching the tie-down chains and the pilot asked me why. The winds were calm, after all. I said that I just felt more comfortable if the wheels were chocked and the tie-downs secured. I think he thought I was full of hot air. As we ate lunch in the airport restaurant, looking out on the ramp where our aircraft was parked, we were both surprised to see a CDF Huey helicopter descend on a nearby taxiway to drop off some fire fighting personnel. As the Huey hovered closer and closer to the ground, all of the planes on the ramp began shaking and bouncing in their parking spots, creating an unexpected, teachable moment.

4 comments:

Colin Summers said...

John Wayne Airport (Irvine, CA) is a great place to teach some of those points. Large jets are mixed with tiny training aircraft. When I went down for one lesson there they did an hour of ground school on where to be, where not to be, and would could happen if you confused the two.

Greybeard said...

Point spot on, John!
About the helicopters, I mean....
The Jet A pumps are frequently co-located with the AvGas pumps, so if I come in and need a spot of fuel and find several airplanes sitting at the pumps, what am I supposed to do? I may need a quick turnaround for a critical patient.
I know, it's not a normal occurrence.
But it's happened to me more than once, at more than one airport.

(A buddy in a Huey once put a 150 on its' back..... your tax dollars at work!)

John said...

Hey Greybeard,

Not sure what to tell you. If it's a towered field, I'm assuming the ground controller will tell you where to hover taxi and land. If it's an urgent situation, let the ground controller know. You may have to land, walk over and explain the situation to aircraft at the fuel pumps and get them to move.

If it's a non-towered field, I'd broadcast my intentions on the CTAF. Let the other pilots on frequency know that it's an urgent situation. If they aren't on frequency, again you'll need to land a safe distance away, then walk over and tell them the situation.

I've not seen this sort of conflict at airports where I operate since I mostly see R22s and R44s. The occasional lifeguard or Coast Guard Dauphine or police Hughes are usually fueled from a truck, not at a self-serve pump.

Must be a hassle for you when this sort of things happen ...

Aviatrix said...

In Canada you have to memorize a bunch of distances behind aircraft of various sizes at ground idle and take-off power before you can fly solo. Problem is that the distances you have to memorize are given in feet, and a young Canadian hasn't a clue how long they are.