IF YOU were standing on the flight ramp at any of the twelve-score major airplane delivery points, and watched the crew chief direct the pilot through the final pre-flight checkout you would see him drawing imaginary circles in the air, smoking invisible cigarettes, sucking his thumb like a baby and ending up by cutting his own throat. Don't bother calling the wagon! The crew chief is merely giving the pilot directions on final checks and adjustment before the ship takes off.
Over the roar of the engines, it would be impossible to shout clear communications to the pilot. In many modern transports and bombers, he sits nearly a full story above the ground. Attempts have been made to utilize the ship's radio system, but that put unwarranted tax on transmitting equipment, was more mess than it was worth. Temporary telephone hookups suffered the same fate, and crew chiefs went back to aviation's oldest means of inter-crew signaling hand signs.
Handies are as old as is flying itself. Orville Wright gave Wilbur Wright a hand signal at Kitty Hawk when the frail powered kite strained at the monorail rig. A simple dropping of the raised hand signaled Wilbur to drop the weight in the catapult tower, and launch a new era in transportation.
Since then, hand signals have been used, both in the air and on the ground, an absolute, unmistakable method for transmitting information over the roar of the power plant.
The first set of standardized gestures were used by flying instructors in open training planes. They were fairly simple, and were designed to be viewed from the back as the student universally sat in the rear cockpit in a tandem-seating trainer. A simple pointing up or down, usually with the right hand extended over the shoulder where the student could see it plainly, meant raise or lower the nose. If the hand were extended sideways, palm up, with a "push it up" gesture, it meant raise the wing on that side. A lowering movement meant put the wing down.
The flat hand, held vertically, making a fairly wide sweep of the horizon, usually meant rudder movements; pointing the ship's nose on the horizon. In the famed Gosports schools in England, speaking tubes were installed early during the last war, but even there, many instructors preferred hand signals. Our modern trainers are, of course, equipped with interphones, built as an integral part of their communications system, but there are still plenty of instructors who prefer "handies."
The best explanation for this came from one veteran sky prexy who is making future Army aces at a well-known Southern contract school. He says "Current Army instructor's manuals preclude profanity between instructor and student. With the 'handies,' it's impossible to cuss."
As the use of handies in flying instruction diminishes, use on the ground increases as the airplane becomes more complicated. There was a time when hand signals were used only to guide the airplane on the ground while taxiing close to parked objects, or to bring planes to an exact place of the operating line.
The crew chief walked in front of the plane, to one side, so that the pilot could see him, and usually backwards, with his face toward the approaching plane. Both hands held in the air and a rearward motion meant "Come ahead," palms forward meant, "slow down to a stop," hands crossed meant "stop quickly."
Pivot signals varied a little from field to field, but they were all in the same spirit, a plain indication of a turn.
The complex job of final check-out of new airplanes has evolved almost two score new hand signs, many of which are becoming standard throughout the industry. Douglas Aircraft at Santa Monica has standardized about thirty of them, and they are rapidly being accepted throughout the United Nations as the American Indian's sign-language was universally accepted among the red men.
One of the old signals, still in use, is the simple drawing of rapid circles in the air a plain gesture for "raise the RPM." (revolutions per minute) or turn the engine faster. Making a circle by joining the thumb and forefinger means "lower the oil pressure". Several possible reasons for this are extended. It may have originally meant "bring the oil pressure back toward zero".
If the right fist is clenched and the left palm held lower, parallel with the ground, it means, "raise the fuel pressure". If the index finger is held under the middle finger, it indicates that the pilot should set the vacuum in the engine nacelle.
Setting proper fuel-air mixtures has developed a grammar all of its own. Because the pilot cannot observe the color or smell of the exhaust gases, he must depend on the crew-chief's observations. If the engine is running on too lean a mixture of fuel and air, the exhaust gas actually irritates the eyes. This is an old axiom among line mechanics, so the signal is "tears", holding the hands to the eye corners. "Make it richer" signals the crew chief, by holding three fingers down and facing the other palm up. If the pilot overdoes it, the ground man motions as though he were smoking a cigarette this means that the exhaust is smoking, because the mixture is too rich. Some crew chiefs signal too lean a mixture by holding their nose. Combustion of too thin a mixture of gas and air is actually no perfume.
Most of the signals are fairly obvious mimicking of the actual motions that the pilot must perform. For instance, if the crew chief wants the pilot to pull out the battery plug, he inserts his forefinger into his vertically clenched fist and briskly withdraws it, just as the plug would be withdrawn from the receptacle. Removal of the landing-gear pin is a similar operation, performed in the horizontal plane, so the gesture is the same, performed flat-wise.
In the same class comes the signal for setting the parking brake, where the crew member actually sits on the ground (parks) and goes through the pantomime of setting the brake. "Close the hatch", is shown by pointing to the one which needs closing and pulling down briskly with both fists. A wide "push it up" motion with the raised palms means "raise the bomb-bay doors".
A little more obscure are the mechanical and instrument signals. De-icer sequence signals are generally prefixed with a finger (usually from the left hand) held in the mouth. The number of fingers on the right hand raised, shows the number of de-icer sequence the crew member wants to see tested.
Simple letter signals, made with the fingers are recent additions. V stands for vacuum adjustment. The letter A made with the inverted V finger signal, crossed by the forefinger of the opposite hand shows that hydraulic pressure adjustment on the automatic pilot is required.
Daily the number of gestures increases. Each point that requires adjustment while the power plant is in operation, eventually creates a handy of its own. For instance, pilots checking compasses at Douglas get hand signals for ship-compass-rose corrections.
With all the sign-language evolution, one bloodthirsty gesture has become universal. When the crew-chief slides his forefinger murderously across his own throat, it's neither threat nor suicide it merely means, "kill that engine".
This article was originally published in the January, 1944, issue of Air News magazine, volume 5, number 6, pages 14-16.
The PDF of this article includes 16 captioned photos illustrating various hand signals and three photos of a ground crew man communicating by sign with the cockpit of a C-47.
Photos are credited to Monkmeyer Press.
The original was printed on 10½ by 13½ inch paper. The images in the PDF have been reduced to fit on standard A-size paper.