The term:

“angle of the dangle” refers to the angle that the tow rope drops when you can’t see the tow plane. If you fly the so called angle that should put you above the prop wash and straight behind the tow plane even in a slow turn. -Lt. Col. George I. Theis

The problem:

Late in 1942, some CG-4A pilots found themselves being towed in the dark or in clouds (called instrument flying conditions) with only a short length of towline visible. The pilot’s inability to see the orientation of their glider behind the tow plane had disastrous results on several occasions, especially because the pilots had no special gauges for instrument flying. To rectify this, the research staff at Wright Field helped develop a special instrument that was designed to show the angle of the rope, near the glider, and extending from the tow plane. Using some words already in use, the pilots soon called this device the “angle of dangle instrument”...(Grim 115)

The solution: The Indicator

Cable Angle MkIII was sometimes known as the “angle of dangle”, and was fitted to gliders during the Second World War. Early versions had a single dial which showed the position of the glider relative to the tug, both horozontally and vertically, and was operated by the tow-rope. The coupling between the tow-rope and the indicator needle was mainly mechanical, but later forms of the indicator were coupled to an artificial horizon, as in the MkIII, which to some degree anticipated lateral displacement so that control corrections could be made before it became serious. The Indicator, Cable Angle was the only device perfected at the time which enabled the tug and glider combination to fly in cloud or at night, but its main disadvantage was that sudden slackening of the tow-rope would temporarily give erratic readings. (Imperial)

Four CG4As gliders were picked up in Kansas to be ferried to Laurenburg-Maxton AAFB in North Carolina. This was glider Instructor 2nd Lt. Arthur C. Furchgott’s and his student co-pilot S/Sgt. Martin T. Laffey’s experience with not being able to see the towship. (Dashboard sign in glider reads “Towship not to exceed 120 MPH”)

...Off we went at about 6,000 feet for about an hour before running into a solid overcast. Knoxville had a 300 foot ceiling by then, and the moon was rising. As we circled in a holding pattern near the field two civilian airliners joined us. Due to a shortage of fuel, the towpilots decided to try an instrument approach with the gliders in tow. Now that’s something every GP ought to do at least once, i.e. try the angle-dangle meter approach. ... First towship and glider disappear into the overcast. About 15 minutes later our towship lined up on the beam and started down. From that point on it was one wild ride...We were in the overcast immediately and it was necessary to judge the CG-4A’s attitude by looking at about four to five feet of towrope. The airspeed began to go up to 120-140-150-160 MPH and the rate-of-descent went from 200 to over 1,000 feet-per-minute. The tow rope was vertically flat across the windshield and actually under the glider. We must have been directly over the towship at that point. The CG4A was shuddering and shaking like it was about to disintegrate. I shouted to Martin Laffey to get ready to bail out as I thought the wings were going to come off. Martin Laffey reached for the tow-release lever and glanced at the airspeed. It was close to 170 MPH. At the same time he cut loose we broke out under the overcast right over the airport which had boundery lights but no floodlights. We circled to lose speed, landed, and pulled off by the first glider. (Smith)

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SOURCE:

GRIM, J. Norman, To Fly the Gentle Giants: The Training of U. S. WW II Glider Pilots (pg 115). Authorhouse. 2009 pp. 115

SMITH, Doug, Glider Pilot (82nd/436th); Excerpt from Down and Gone, published in the November 1976, SWM Newsletter.

Imperial War Museum, Vehicles, aircraft and Ships:Indicator Cable Angle MKIII, AM REF 6A/1708 html: http://www.iwm.org.uk/collections/item/object/30000161