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Combat Blade Damage

23 September 2017

Dr. Charlton Stanley recently began an interesting on-line conversation of battle damaged propellers and we thank him for this inspiration.

On 26 December 1967 Lieutenant (junior grade) Bruce Marcus’s Douglas A-1 Skyraider launched from the USS Coral Sea on an armed recce mission and met with success in finding the enemy! The Skyraider was struck by antiaircraft fire including the armored windshield but the hole in the propeller blade wasn’t discovered until Marcus landed and secured the engine [displayed in National Naval Aviation Museum]—© Travel for Aircraft/Joseph May

A close view of Lieutenant (junior grade) Bruce Marcus’s Douglas A-1 Skyraider battle damaged prop blade—© Travel for Aircraft/Joseph May

Rotor blade tip cap of the MH-60 Seahawk known as “Skat 14”, signed by the rescuers and rescued, showing small arms fire evidence during the rescue of SA-3 Goa downed “Hammer 34” on 02 May 1999 over Serbia [displayed in the USAF Armament Museum]—© Travel for Aircraft/Joseph May

A close view of the hole made by an antiaircraft round through Skat 14’s rotor tip cap. “Hammer 34” was pilot Lt Col David Goldenfein of an F-16 Fighting Falcon and later became Chief of Staff of the U.S. Air Force in 2016—© Travel for Aircraft/Joseph May

 

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2 Comments leave one →
  1. 25 September 2017 01:28

    Thanks for the credit. I have decided to embark on a search of old wartime photos, looking for prop damage.

    When I first bought my C-177 Cardinal, the logbooks showed the constant speed prop was way past due for an overhaul. After shipping it off the the prop shop, the shop manager called me. He said the blades were in good shape and simply needed to be dressed, balanced and repainted. The hub was another story. It was eaten up with corrosion and beyond repair. Uh-Oh. Time to get out the checkbook. He told me a bit about props and hubs. During the conversation, he asked if I knew how much stress and strain was on the hub at takeoff power.

    I did not.

    He went on to say there are two vectors on the hub. Straight ahead horizontally as the hub has to pull the aircraft forward. The other vectors are at 90º to the thrust line due to the centrifugal force exerted by the mass of the spinning prop. At takeoff RPM, he said the blades on my little Cessna weigh about 40,000 pounds. That is the weight of a fully loaded 18-wheel truck. 20 tons.

    Imagine that load being placed on engine mounts if the prop hub gives way with one prop departing the airplane, and the other remaining attached.

    If a prop has a chunk taken out of it, the risk is great. The unbalanced prop may try to shake the engine loose from its motor mounts, or shake the airframe so much things break and the plane becomes uncontrollable. There are jokes about how is it those airplanes could get airborne with all that brass on board.

    • travelforaircraft permalink*
      25 September 2017 21:31

      The physics of flight! If I were to teach Physics 101 I’d use bicycles and aviation examples.

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