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Anti-icing feed shoe span

Aviation Mechanic Powerplant (AMP) practice question 9 of 10 on Propellers. ACS element AM.III.M.K9 · difficulty: applied. Want to answer it in a timed quiz? Use the Aviation Mechanic Powerplant (AMP) practice mode.

Question bank updated 2026-09-22

QUESTIONFluid anti-icing feed shoes extend from the blade shank out to about 75 percent of the propeller radius. On a propeller with an 80-inch diameter, about how far from the center of the hub does a feed shoe reach?

  1. AAbout 30 inches
  2. BAbout 60 inches
  3. CAbout 40 inches, the full blade radius
Show the answer and explanation

Correct answer: A. About 30 inches

  • A — correct An 80-inch diameter gives a 40-inch radius, and 75 percent of 40 inches is 30 inches from the center of the hub.
  • B — incorrect This takes 75 percent of the 80-inch diameter instead of the radius, which would place the feed shoe well beyond the blade tip.
  • C — incorrect Forty inches is the whole radius; the feed shoes stop at roughly three-quarters of that distance, short of the tip.

BACKGROUND

Ice on a propeller blade distorts the airfoil section, causes a loss of efficiency, adds weight, and because it collects asymmetrically, produces unbalance and destructive vibration. A typical fluid anti-icing system has a tank, a pump whose rate can be varied with the severity of icing, and a stationary nozzle that delivers fluid into a U-shaped slinger ring on the rear of the propeller assembly, from which centrifugal force moves it through nozzles to each blade shank. Because airflow around the shank tends to disperse the fluid away from where ice collects, rubber feed shoes, or boots, are installed on the blade leading edge. These narrow strips run from the blade shank to a blade station of approximately 75 percent of the propeller radius and contain parallel open channels through which centrifugal force carries the fluid outward. Isopropyl alcohol is used in some systems because of its availability and low cost.

STUDY TIP

Read the wording carefully: percentages of propeller dimensions are almost always taken from the radius, so convert diameter to radius before taking the percentage.

KEY POINTS

  • Anti-icing feed shoes run from the blade shank to about 75 percent of the propeller radius.
  • Fluid reaches the shank through a slinger ring and moves outward by centrifugal force.
  • Isopropyl alcohol is used in some anti-icing systems for its availability and low cost.

SOURCES

  • sources/amp-powerplant/ch07.txt "Anti-Icing Systems"
  • FAA-H-8083-32 ch07, Ice Control Systems
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MORE ON PROPELLERS

SkyDrill is not affiliated with the FAA. This is an original practice item based on FAA-H-8083-32B Aviation Maintenance Technician Handbook – Powerplant, and 14 CFR part 43. Regulations and handbooks are revised; confirm details against the current edition.