Another narrative from Jack Abercrombie on the early days of the F-15 Eagle project, A first hand account of the F-15 Spin Test Program. This narrative is part of Jack Abercrombie’s memoirs. Jack was an Aerodynamics Project Engineer from 1971 to 1978. Credit: Jack Abercrombie
Download here or here or here (12.3 Megs)
Additional blog info supplied by Jack Abercrombie here
Another narrative from Jack Abercrombie on the early years of the F-15 Eagle project, An exciting first hand account of the F-15 design program with all it’s warts. This narrative is part of Jack Abercrombie’s memoirs. Jack was an Aerodynamics Project Engineer from 1971 to 1978. Credit: Jack Abercrombie
In 2012, Jack Abercrombie wrote several articles and a slide show to commemorate the 40th anniversary of the F-15’s first flight. They detail the challenges of bringing along a new aircraft and the changes that were required to the airframe to enable it to be the world class fighter that it became.
This is a must read for anyone who is interested in the F-15 Eagle and it’s history from the man that was there! Jack was an Aerodynamics Project Engineer from 1971 to 1978. Credit: Jack Abercrombie
Download here or here or here or here (2.6 Megs)
Origal post (More info) here
A fascinating first hand account of the F-15 Eagles first flights and the problems that had to be solved. This narrative is part of Jack Abercrombie’s memoirs. Jack was an Aerodynamics Project Engineer from 1971 to 1978. The first picture above shows most of the engineers at Edwards who supported the F-15 first flight. Credit: Jack Abercrombie
On a personal note, I ran one of the wind tunnel tests at Langley that resulted in the “Snag” horizontal mentioned in this memoir!
A note from Jack Abercrombie: Ron--The F-15 Development Summary recently posted is an early version which contains a typographical error which I later corrected. The "First Achievement of Mach 2.5..." shows a date of 23 August 1973. The date should be 13 August.
The newspaper article comes from Jack Abercrombie who has this to say: "My first job after graduation was as an aerodynamicist on the C-132 at Douglas Tulsa. The very day before reporting for work, the newspaper in Tulsa reported the contract cancellation. What an interesting way to start a career."
Credit: Jack Abercrombie
Jack Abercrombie wrote in response to this entry: “The gear being down was not intended for the entire flight. On the first gear retraction attempt, one door jammed.”
He goes on to say:
"During this time, we in the T/M (Telemetry) room had our eyes glued to the orange graph paper with blue ink strip charts rolling by so fast it was impossible to immediately assimilate all the data. Except for the airplane’s left main gear door which refused to close all the way (resulting in conducting an alternate, gear-down test plan), there were no major surprises in the airplane’s behavior during the first flight." Thanks, Jack!
Original post here
Jack says: “Here's an ad from a 19 April 1976 Aviation Week showing the then (early) F-18 configuration. Note the scaled-up YF-17 LEX, three LEX slots, wing LE snag, short-span ailerons, stabilator with no snag, and strakes on the sides of the nose radome.” It is very interesting to compare this to the later as-built configuration. Enjoy!
![Strakes and Fences3[6]](https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiX2P41KEUnt3SJeVsFHdtRzjbKbQdXXmhLOK2wnlqVAD3pwA2yhkCBEbY7dT7hjDpIrwpMyufnRyqfHiwXMOWG3VSyDn6scy9lCjFw3ttNgl72oXHDgr8BcZKtMeH1nu9mE8VFyuWPH90/s1600-h/Strakes%252520and%252520Fences3%25255B6%25255D%25255B6%25255D.jpg "Strakes and Fences3[6]")
Jack Abercrombie was in the middle of this problem and had these words:“The attached document describes the buffet problem and the solution. Not noted is the fact that the first "clipped tip" for the airplane was achieved at Edwards in the dark of night by sawing off the tip, smoothing the ragged edges with wooden tips and duct tape. And, it worked wonders! The alternative was to incorporate a combination of strakes and fences (a St. Louis developed configuration)--unfortunately, the alternative resulted in too much drag to be viable. Both configurations are shown in the above sketches.”
My only part in this as a Flight Test Engineer was to coordinate the production, distribution and delivery of the Mod Kits sent out for incorporation in all of the pre-production aircraft.
No matter if you call them clipped, modded or raked wing tips, Jack has written a very interesting saga about their history!
Jack Abercrombie found some of his old memos and charts from his time as the McAir Chief Aerodynamics Engineer.
As Jack says: “I found some of my work from many years ago regarding the the NACA Rocket Model F4H-1. Apparently, after the test of Memorandum RM SL57K20, there were at least three more tests the following year (1958).
In 1983, after I became Chief Aerodynamics Engineer, one of the old time VPs remembered the NACA tests, and I was asked to dust off the results. I had extensively examined the NACA data more than 20 years before during a drag investigation when I was still a working Aerodynamicist. My archives from the earlier period were used to generate the data for the attached memorandum 341-83-313 dated 8 Nov 83.
Note that the rocket model derived data is really no good, particularly subsonically. Supersonically, the data are better but still not good.
The memo 341-83-313 was presumably passed on; but, I never heard any more on the subject.”
I have also included a nice photo of a rocket boosted Douglas F4D model. So, this type of test was run on several aircraft models!
Ron Hinkel reports that: (I turned up at China Lake Naval Weapons Center as the newly appointed Air Weapons Officer and Agile Project Pilot in October 1973. The AIM-95 Agile was an air-to-air missile being developed as an advanced replacement for the AIM-9 Sidewinder short-range air-to-air missile. The Navy intended it for the F-14. The US Air Force was developing the AIM-82 missile to equip the F-15 Eagle at the same time. Since both missiles were more or less identical in their role, it was decided to abandon the AIM-82 in favor of the Agile.)”
Jack Abercrombie reports that the program had been canceled in 1970. “The Chicago Tribune in Sep 1970 reported the cancellation of the AIM-82: http://archives.chicagotribune.com/1970/09/03/page/7/article/missile-work-is-canceled-by-air-force . To my recollection, MCAIR never did any wind tunnel testing of the AIM-82/F-15 configuration.”
“Since the F/A-l8 fighter-attack aircraft made its first flight in November L978, some significant changes have been made to the control system to improve flying qualities characteristics. This paper covers some of the highlights of that flying qualities development, touching briefly on the initial design criteria and the evolution of the control system as we progressed through the flight test program. Particular emphasis is placed on some unique and very innovative features of the flight control laws.”
Click here for a short slide show presentation of this report
After spin testing it was leased to NASA at Edwards AFB, CA. in 1985, to be Used in high angle of attack and thrust vectoring tests. It was registered as N840NA and Flown as 840. After it finished with NASA, it was sent for display to Virginia Air And Space Centerat Hampton, VA, March 2003.
Per Jack Abercrombie: “ FYI, the MCAIR test pilot in the last three photos is Denny Behm, the designated high AOA/spin test pilot for the program. (Denny was also the guy who flew the first spin in the F-15 Eagle a few years before--although not planned).”
Click here to download a very more F-18 spin Movie (.7 Megs)
BTW: The other two are the clipped wing tips (covered below) and the notched horizontals.
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![Scan1206[2]](https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiwPniceGmuWfaGr-2RfG8Z26X9vMD2MdXUiaWk5JiPGrG22vHz6TLL8aQFx9jm3Ezl9U78zpFotLbl7LOH1nzgW79VfKWeb-ssdhAI7T48P_8m8gduKKiRcVduGiERweU_z1g9fAPCM1w/s1600-h/Scan1206%25255B2%25255D%25255B2%25255D.jpg "Scan1206[2]")
