Taxiing with asymmetric thrust...

[cagarini]

One aspect / detail that captured my attention was the result of taxiing with asymmetric thrust in PSX.

Say that I shutdown #1, or even #1,2, or even #1,2,3 :-)  (*)

If the aircraft is "light" enough, at idle thrust I will practically not have to use tiller to steer straight along the taxiway.

Of course if thrust is required, and with only two, or even only one engine it sometimes has to be set at much higher values than with all of the 4 engines alive, steering can become required.

Is this due to the excellent weight and moment distribution among the undercarriage of the 744, possibly in combination with some sort of auto-locking mechanism of the front gear when the steering tiller is not being used ?

(*) just out of curiosity, should it be #4, then #3 and maybe also #2, but never #1 because of the Hydraulics ?

[emerydc8]

(*) just out of curiosity, should it be #4, then #3 and maybe also #2, but never #1 because of the Hydraulics ?

For us, it's usually #3 first, or #3 & #2. However, there were times at certain bases in Afghanistan where the taxiway was so narrow that we would shut down #1 & #4 to keep from sucking up all the FOD. I wouldn't taxi with anything less than two engines.

[cagarini]

(*) just out of curiosity, should it be #4, then #3 and maybe also #2, but never #1 because of the Hydraulics ?

For us, it's usually #3 first, or #3 & #2. However, there were times at certain bases in Afghanistan where the taxiway was so narrow that we would shut down #1 & #4 to keep from sucking up all the FOD. I wouldn't taxi with anything less than two engines.

Thx for the answer emery :-)

[cavaricooper]

(*) just out of curiosity, should it be #4, then #3 and maybe also #2, but never #1 because of the Hydraulics ?

For us, it's usually #3 first, or #3 & #2. However, there were times at certain bases in Afghanistan where the taxiway was so narrow that we would shut down #1 & #4 to keep from sucking up all the FOD. I wouldn't taxi with anything less than two engines.

Jon-

Here's one resurrected from the ashes... landed in Denver today, in the middle of a fairly heavy snow shower.  With all the accumulated snow and ice, I was gingerly taxing back to south cargo, when I thought I had better shut down #2 as well (to avoid any unneeded braking).  Have there been changes in this venue?  I know BA shuts down #3 fairly routinely (Peter?) for fuel savings, but I re-read your bit about shutting down #1 and #4 with interest, because purely from a FOD perspective, it makes the most sense.

I also remember reading something from you about hesitancy to automatically shut down engines, in case of rising ramps, taxiways etc. The PSX RB211s generate enough residual thrust that without at least one shut down, I am constantly accelerating to 20kts, then braking to 9 or so and repeating.... what is the current 744 fleet mindset (if you can tear yourself from your love affair with errant EADIs )?

Ta- C

[emerydc8]

Hi Carl.

I don't have access to our 744 manuals any more, so I don't know what the latest policy is for shutting engines down. I don't imagine it has changed much.

It's funny that you mention the cargo ramp in DEN  (the one just to the left of the approach end of 35L). I once slid down that taxiway in a DC-8 using reversers as the only means to control the aircraft. Think about the effect that shutting down an inboard engine would have in a situation like this. That taxiway is pretty steep and in the winter it gets slippery. My personal position is that I am almost never in a hurry to shut engines down. To be honest, most of the guys who are preoccupied with shutting engines down after landing are either management pilots or pilots trying to get brownie points to be management (trying to show that they care about saving money on fuel). Usually they miss a number of important things on the taxi in while they secure the engine(s) and a lot of times they end up burning more fuel because they have to push the existing engines way up to make a sharp turn they weren't anticipating. Just my 2 cents.

[Magoo]

Where I work we tend to shut  engines 3 and or 2 for fuel saving measures, taking into account the aircraft's weight, local knowledge of uphill taxiways, crossing active runways and local authorities as some airports do not allow this procedure. It saves a fair bit of fuel in the long run!