b377 -
If I ever meet you, you will owe me a few lagers...!
Scratching my old head here, hoping not to tell you wrong.
Hopefully some other friends will assist as well.
Ok - 707-720 can have eiher...
xxx
(1) Large ventral fin... no other way to define it -
It was found on ALL old "straight pipe" 300 and 400s.
Also found on the "early 300B with fan engines" with 17 flaps takeoff setting.
And finally on 100s which had JT3C engines... ex. TWA 707-131
Purpose - improve lateral stability, and prevent over-rotation.
Note that the very first 300s had a shorter tail fin.
UK CAA required a taller fin (read D.P. Davies) + VF for lateral stability improvement.
Boeing made it standard on all early 300s and non-fan 100s...
xxx
(2) Small ventral fin -
Was found on all 720, and 100 with fans -
Purpose - limit damage to fuselage in case of over-rotation.
Stall warning (stick shaker) did not operate early enough.
xxx
(3) NO ventral fin -
Only on 300B-Adv, 300BAH (B-Adv-Heavy) and 300C.
All of these were airplanes with full set of leading edge flaps, and 14 flaps for takeoff.
Stick shaker operated much prior reaching over-rotation attitude.
By the way - these got changed from "parallel" to "series" Yaw Damper.
xxx
Are you giving me an oral exam for 707/720 TR...?
My type rating is somewhat rusty, sorry.
Hope you passed me with colors.
xxx
Happy contrails
P.S. - Thanks 411A - Forgot the "size" of these ventral fins.