Ask the Captain: Making time on the taxiways

Question: At airports with very long taxi distances, such as Denver International, do pilots taxi faster than normal? What is a typical taxi speed?

— Submitted by reader C. Beiderbecke, Illinois

Answer: Pilot taxi speed normally does not increase with taxi length. In some cases when brake heating is an issue, pilots will let the taxi speed increase more than normal to keep from "riding" the brakes, thus causing heat. Some airplanes and operators have maximum taxi speeds posted.

Though it can vary, a typical speed would be about 20 knots on a taxiway with nothing nearby.

Q: Is there a speed limit for planes while taxiing on the runway? Planes in Germany seem to taxi a lot faster than they do in the U.S.

— Ken Duval, Germany

A: Some airplanes, such as the 747, have limitations on taxi speed, but most do not. Operators often incorporate ground taxi speed limits, which vary from operator to operator.

I have not noticed a significant difference in taxi speeds between Germany and the USA.

Q: I see planes "wiggle" their flaps before taxiing and after landing, what are the reasons behind that?

— Inray, Taiwan

A: To make sure that flight controls move properly before flight. What you are seeing is the ailerons, spoilers, elevators and rudder being exercised. The flaps only move from the retracted position to the proper position for takeoff.

Q: Why did they change the radio language from "Taxi into position and hold" to "Line up and wait?" I liked "Taxi into position and hold" better.

— Roy Bazylewicz, Tucson

A: "Line up and wait" is the international standard phrase. Only the USA used "Taxi into position and hold." It's a good step to standardize phraseology to the international standard, which was set several years ago. Many U.S. pilots fly internationally. This change reduced the chance of a misunderstood clearance.