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Ask the Captain: Why are hurricane hunters propeller-driven?

Question: Why are the hurricane hunter planes only twin turboprops and not the regular fan jets that passenger planes use?

— Submitted by reader Edward Zell, Ohio

Answer: The turboprops are more tolerant of hail than the jets. Airplanes that penetrate thunderstorms have an increased chance of encountering hail. Additionally, the two types of airplanes used, the P-3 and the C-130, are especially rugged.

Good question!

Question: Why are the hurricane hunter planes only twin turboprops and not the regular fan jets that passenger planes use?

— Submitted by reader Edward Zell, Ohio

Answer: The turboprops are more tolerant of hail than the jets. Airplanes that penetrate thunderstorms have an increased chance of encountering hail. Additionally, the two types of airplanes used, the P-3 and the C-130, are especially rugged.

Good question!

Q: Regarding the recent column about a jet engine using reverse thrust for landing: How does a propeller engine slow the plane?

— M. Pengilly, Ohio

A: The propeller is rotated so that the prop wash (thrust) is directed forward. There are two advantages for the propeller aircraft. When the propeller is flattened out from the flight idle position, it creates a large amount of drag. Further rotating the propeller blades reaches a point where the airflow actually is opposite the direction of travel.

Propeller airplanes can land on short runways due, in part, of the effectiveness of the propeller reversing.

Q: Is it normal for small regional turboprops to shake very badly just before and during takeoff?                       

— Josh, Peoria, Ill.

A: Some turboprop aircraft change the speed of the engines for flight and use varying pitch of the propeller, causing some vibration on the ground or just prior to landing.

The direct answer to your question is: It depends on the type of airplane and the conditions. Vibration levels of turboprops are higher than for jets, so you may notice the increase more. 

Q: Why do winged airplanes use engines with twin propellers spinning in opposite directions?

— James R. Gammage, Sharpsburg, Ga.

A: This increases control during flight with one engine inoperative. Propeller discs (a spinning propeller acts as a disc) produce thrust asymmetrically due to aerodynamics, and by keeping the most efficient part of the disc closer to the center line of the airplane, control is enhanced. 

John Cox is a retired airline captain with US Airways and runs his own aviation safety consulting company, Safety Operating Systems.

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