Human Engineering And Aircraft Seating By Jim N. Gladney 412 Norma St., Ridgecrest, Calif. 93555 TTWIDENTLY THE DATA on human engineering used 1_J by industrial designers and others is not generally known or available. I have attempted to present information pertinent to our interests, so that we will have not only good looking craft but functionally good ones. Let us consider the cabin or cockpit as a seating package. This package should accommodate people ranging in size from 95 pounds to over 200 pounds; being 4 ft. 9 in. tall to 6 ft. 2 in. tall.
The center of gravity of the human will vary slightly according to weight/build, but we can assume from 0.5 in. to 1.6 in. above the pivots of the femur-pelvis junctions. The body consists of three masses, plus the limbs. The head with: 15.9 pounds maximum; 13.2 pounds median; 10.5 pounds minimum. The rib cage with: 32.45 pounds maximum; 26.9
pounds median; 21.4 pounds minimum. The pelvic girdle with: 53 pounds maximum; 44 pounds median; 35 pounds minimum. The limbs with 50 percent of the weight: The upper arms: 11.4 pounds each maximum; 9.4 pounds each median; 7.5 pounds each minimum.
The lower arms: 3.7 pounds each maximum; 3.1 pounds each median; 2.5 pounds minimum. The hands: 1.4 pounds each maximum; 1.15 pounds each median; 0.9 pounds each minimum. The upper legs: 20.1 pounds each maximum; 16.61 pounds each median; 13.2 pounds each minimum. 8
DECEMBER 1967
The lower legs: 9.85 pounds each maximum; 7.17 pounds each median; 6.5 pounds each minimum. The feet: 2.9 pounds each maximum; 2.4 pounds each median; 1.9 pounds each minimum. If possible, this package should hold its occupants so that at least the pilot's eyes are nearly in the same spot with his hand on the stick or wheel remaining in about the same place. (We can make the seat and the pedals adjust easier than the stick). The recommended angle between upper, or femur, and the lower leg is between 120° and 155°. Leg angles too near 180° pull the Satorius and Gracilis muscles unnaturally; few of us are Yogi addicts. Holding the leg parts too near acute angles increases the cabin depth needed and lessens the leverage we can exert upon the pedals. Since 50° is maximum for head deflection, the supine position one assumes in some sailplanes and Grande Prix cars seems too much like the rack. Eye movement beyond 15° becomes less efficient. The PRPA justly says that 5° from the horizontal line of sight should be unobstructed ahead of the pilot. 15° each side of straight ahead is the best, beyond 30°, color and other perception deteriorates. The head pivots 180°, giving 210° possible vision. The miniscule windows on some cabin planes look ugly, cheap, and small beyond all justification. Here again, the PRPA stipulates peripheral vision of 130° to each side of the forward center line.
Though the near straight arm, two o'clock, eight o'clock position on the wheel still holds good for competition driving, we won't have our hands that high, with the weight and energy of one hand balanced by the other. The mike, throttle, flaps, etc., will keep one hand busy just when we most want the balancing effect of that hand on the wheel. As the sketches show, we need a seat which will adjust six inches horizontally, six inches vertically and pedals which will adjust eight inches horizontally. The seat cushion should be 13 in. by 16 in. minimum; 17 in. by 19 in. maximum, the width greater than depth. The resilience is more important that the uncompressed height and here lies a problem. A 95 pounder and a 200 plus pounder using the same foam cushion. Compound density cushions may help. The cushion should be at about 22° for a big man and about 15° for the small one. The seat back should be 12 in. by 18 in. minimum; 25 in. by 22 in. maximum unless it tilts to 110° or greater, then the 18 in. to 22 in. dimension should change or the head be supported by an additional headrest. With the stick full back, seat full back, we should allow 12 in. for the body. Seat forward, stick full back, we should allow eight inches for the body. Seat full forward, stick full forward should allow for a reach from the shoulder pivot of 23.5 in. The pivot on a small pilot might be 20.5 in. above the seat, seat compressed and four inches in front of the back cushion. Pedals should be 1 in. by 3 in. minimum, 3 in. by 4 in. maximum; two to six inches apart. A pedal bar should be 14 inches long minimum; the feet four inches out from the bar's pivot point. Normal pedal travel should be five inches; seven inches maximum utilizing leg action, 2.5 in. maximum for ankle action only. Again, pedal adjustment is 11 in. The ankle can exert 20 pounds; feet, ten pounds per foot up to 50 pounds if leg is used. Pedal movement should be nearly parallel to the lower leg and at right angles to the foot. Pedal pressure should concentrate at the ball of the foot. Shoes for a 6 ft. 2 in. man should be 4.5 in. by 11.75 in. Cold weather flying in open cockpits will require .7 in. thickness for heavy flight gear all around and a
can probably go within an 88 in. length. Side-by-side seating would need 44 in. across.
Surveys of military and airline pilots have been
made. This and much other information has been used by Douglas, NAA, Boeing, etc., and the industrial design organizations advising them.
Seating is far from solved; being suspended in a
nylon fish net wouldn't vary the pressure points much for Jim Bede though his weight wouldn't be 90 deg. on his ischial tuberosities as ours is when we're seated. Pulsating cushions aren't very satisfactory. No effort has been made to allow for parachutes, doors, hatches, or seat frames in this article but surely quick release pins on an adequately large panel should be provided for bail out emergencies. An 18 in. by 24 in. hatch is minimal, one 24 in. by 36 in. is good. Adequate clearance between the seat and hatch edge is necessary to assure egress. Eight inches should be sufficient. We have little choice in the instrument faces we use but knobs, levers, and wheels can be selected to an extent. Consider identification, leverage, size (gloves in an open cockpit?). REFERENCES:
There are extensive bibliographies listed in the latter two references; some of these relating to equipment design or human dimensions. Railway Study—Heywood-Wakefield Co., Gardner, Mass. Studies by E. A. Hooton of Harvard, 1945. Auto Seat Cushions—SAE 45-26-39, 1938 by C. A. Tea Riding Comfort—W. E. Lay, L. C. Fisher, SAE trans. 47 (5) 482-496, 1940.
Seat Cushions and Ride Problems—C. R. Paton, E. C.
Pickard and V. H. Hoehn. SAE 47 (1) 273-286, 1940. Product Engineering—"Human Engineering, 14 reprints."
Dimensions of the Human Figure—Lloyd W. Sahley, Box 3989, Shaker Square Station, Cleveland, Ohio. Design News—Sept. 1, 1966. Selected Body Dimensions of Adults—Series 11, No. 8, Dept. Health, Education & Welfare, June 1965. The Measure of Man—Henry Dreyfuss. Air Progress—October, 1965. ®
maximum of 14.5 in. long by 5.25 inches wide for Arctic
boots. Electric suits aren't yet plentiful. These size extremes cover all adults except the largest five percent and the smallest five percent. So, our seating package for one person should be 56 in. long, 42 in. high and 24 in. wide. Tandem cockpits
JUNIOR MEMBER NEWS A very commendable effort towards coordinating the interests and activities of the EAA junior members is being made in the form of the "Little Guy Newsletter" available on subscription. The newsletter, available at $2.00 for 12 issues per year, is the work of Bill Potter of 8811 W. 102nd St. in Palos Hills, 111. 60465. It features articles and information designed to stimulate and encourage interest and activity in sport aviation, information on other junior members and their projects, and suggestions on how to approach the cost and time factors as they affect their special status. All in all, the "Little Guy Newsletter" fills a very important need in the EAA, and it needs the support of every member, senior as well as junior. ®
(Photo by Jim Tinkler)
Paul H. Poberezny is greeted by EAAers George Goodhead and Ernie Ryder of Tulsa, Okla., on his arrival for fhe E A A / A A A Tulsa Fly-In and dinner October 14 and IS. The P-64 created a great deal of attention with North American Aviation personnel (the builders of the P-64 in 1940) and people of Tulsa. It was examined closely by
many hundreds of people at the very successful fly-in. SPORT AVIATION
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