Monday, July 13, 2015

A-4 Nose Gear Steering

To minimize weight, the Douglas A4D Skyhawk did not have nose gear steering among many other things. Turns on the ground were accomplished by differential braking. It was guided in close quarters and where accuracy was desired, e.g. lining up on the catapult, with a steering bar or "tiller" inserted in the nose wheel hub.

This practice was common for the first Navy carrier-based jets. Nose-gear steering was introduced with the F7U-3 Cutlass because of its size and weight.

When the A-4 was being modified to be a two-seat trainer, one of the features added to improve its marginal crosswind landing capability was a steerable nose gear. This was subsequently adopted on later versions of the single-seat Skyhawk. The changes consisted of a hydraulic actuator mounted in place of the shimmy damper on the right side of the strut just above the fork holding the wheel, hydraulic lines from the nose wheel well to the actuator, and a vertical sleeve to enclose the hydraulic lines. The sleeve was mounted to the bottom of the strut and guided up and down by a collar mounted on the upper back side of the nose landing gear as the shock strut moved in and out. (The slender rod, aka shrink strut, on the left side of the nose landing gear pulled the shock strut into the strut body as the gear retracted. This minimized the volume required for the retracted nose landing gear.)
The illustrations use crops from a set of A-4M walkaround photos by Bill Spidle.

2 comments:

  1. When the tiller bar was in use during taxiing on the carrier it was important to not use differential breaking as that would tend to toss the poor tiller guy around a bit. A nice even pressure on both brake pedals was the order of the day.

    The most interesting aspect of no nose gear steering came right after a trap. It was much preferred for us to get the plane out of the landing area without the tiller guy having to come out and get us, which almost always forced the next plane into a foul deck wave off, leading to verbal abuse from the Air Boss and/or the ship’s Captain. As the plane was drawn backward slightly due to the elasticity of the arresting cable system it was necessary, while simultaneously raising the hook, to do a little dance on the brake pedals to get the nose gear to caster in the right direction so that when power was applied the plane headed over the foul line and not for the port side catwalk. Once safely over the line the tiller guy picked us up and took us to our parking spot on the bow.

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  2. NWS was of great benefit for our A4Gs aboard HMAS Melbourne, especially when lining up on the 100-110 foot catapult. I distinctly recall the CPO Catapult Director waving - then head nodding - then 'winking' left / right to get us to line up accurately. :-)

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