"Grapefruit"

[Ivo de Jong]

"Grapefruit" was the codename for a special operation on May 28, 1944 and not the name of a type of bomb.
What Fyler is referring to is the GB-1 'glide bomb'. It was a standard M-34 2,000 pound HE bomb, which had 12-foot span glider wings and a tail unit attached. Two of these could be carried externally underneath a B-17. A gyro system in the bomb was supposed to take over control when they were released. It was meant to be a 'stand off' weapon and was to be released well before a well-defended target was reached.
May 28, 1944 saw the first operational use of these bombs. The 41st Combat Wing had three Groups (in all 59 B-17s) equipped with two bombs each and despatched them to attack the huge marshalling yards in Cologne. The drop was a total failure, with most bombs going out of control and spinning in, and others hitting all throughout Cologne and its suburbs. The bomb was never used again in combat.
All details about the mission are in my book "Mission 376, battle over the Reich: 28 May 1944", published by Hikoki and still widely available.
Hope this helps,
Ivo de Jong