SAFETY IN THE AIR

Evening Post, Volume CIX, Issue 25, 30 January 1930, Page 17

SAFETY IN THE AIR

PROTECTIVE DEVICES

PREVENTION OF CRASHES

Tho following article on tho means taken to decrease tho risks of flying, is written by Captain A. G. Lainplugh and Squadron-Leader T. H. England, and is reprinted from a publication of Shcll-Mex, Ltd.

One of the features of the growth and development of civil air transport has been the attention which has been and is being given to devices which will prevent the occurrence, of accidents, or minimise their results. Mishaps arise from many causes, some intrinsically trivial, perhaps, such as the failure or partial failure of the engine through faulty or inadequate petrol or oil supply, or other cause; the development of structural weakness in some part or other through vibrations; errors of judgment on the part of the. pilot; Jlie loss of flying speed when tho machine is near the ground, and many others. Some of these are easily guarded. against, but some, on the other hand, are extremely difficult to detect in their beginnings, though their results .are distressingly obvious.

As is tho case in every form of trimsport,'fresh dangers arise with further development, and tho goal of safety must therefore be kept prominently in mind; this is an even moro urgent necessity with aircraft than for any other means of transport, for what would be si defect of little consequence in say, a motor-car (the plugs oiling up, for example, which could be easily remedied wherever the vehicle might be), might be a matter of life and death for the occupants of an aircraft. Tlje .safety devices used in aircraft may be roughly divided.into four general headings:.

(a) Those for safety in tligbt and . while taxi-ing, (b)' Those for the reliability of the power unit and its fuel supply, (c) Those for certainty in oporation and navigation.

(d) Those for use iv emergencios,

(a) The primary cause of about 80 per cent, of the accidents to aircraft in flight in the past has been the loss of flying speed wheu flying uear tbo ground. "Stalling" (which is the technical term used for such loss of flying speed) is an insidious evil that may arise in several different ways. Tha failure or partial failure of the engine immediately after taking off; tho flying of the machine at too great an angle; turning while climbing—these may easily be followed by such loss of speed that the aircraft is no longer under the control of the pilot, for below a certain minimum speed all control disappears and the aircraft falls in a steep dive (frequently accompanied by a spinning motion), which cannot be checked or interfered with by tho pilot until sufficient speed has been gained in tho descent for the controls to boc.ome operative again. It will- be plain that should the aircraft not be at a sufficient height in the air at the time of the loss of control, the machine

will have dived into the ground and crashed disastrously before it could be brought under control again to fly level.

THE SLOTTED WING.

Now stalling is caused through the loss of lift and increase in drag which occurs when the palnes of an aircraft are at too largo an angle to its direction of movement. Two-thirds of the lift duo to the 'planes are derived from tho negative pressure or suetiou of the air over their upper surfaces when this air is flowing smoothly over them, and this lifting force is wholly destroyed at largo angles of incidence by the airflow over the 'planes becoming irregular and turbulent, resulting in complete loss of control over the aircraft, which then dives, as mentioned in the preceding paragraph. The uso of Handley Page automatic slots enables a pilot to retain control over an aircraft which has "stalled." These are a simple fitment, attached to tho leading edges of the upper planes of an aircraft (if a biplane), and take the form of a small auxiliary aerofoil movable in a forward direction to form a slot between it and the main 'plane. In normal flight the pressure of the air on the nose of the 'plane keeps tho little winglet in close contact with tbe maiu 'plane, the natural contour of which it forms part. As soon as the 'piano assumes too largo an anglo with relation to the direction of tho airflow over it, the forces acting on the forward aerofoil draw it forward away from tho main 'plane, and allow a stream of air at high speed to flow through from underneath, which has the effect of smoothing out the tuibulent air abovo and thus restoring the suction effect of the air.

Tho action of the auxiliary aerofoil is entirely automatic, and does not depend in any way upon the action of the pilot, who, indeed, may not know that his machine is stalling. Aa soon as the machine is on the point of stalling, the automatic slots come into operation; the 'planes therefore do not lose their lifting force, and so there is no tendency for the aircraft to become uucontrollable.

11l addition to preserving control and stability at tho stalling point, the Handley Pago slotted wing also shortens the landing run of the machine to which it is fitted, an invaluable feature should a forced landing have to be made in a restricted space. Tlio unslotted machine in such circumstances would crash into whatever limited the available space boforc coming to a stop, whereas tlic slotted machine would come to rest in time.

BRAKES FOB THE WHEELS.

In this connection wheel brakes for aircraft are also of considerable value in shortening the lauding run, and, in conjunction with the automatic slot, make a remarkable difference to tho length of tho landing run, enabling forced landing to bo made in restricted spaces where heretofore such a manoeuvre would have been absolutely out of the question.

The Palmer piicuuiatie systoni of wheel brakes is very efficient, and is operated by a hand lever in the pilot's cockpit, or (each wheel brake independently) by pedals on tho rudder bar.' This last method greatly facilitates manoeuvring the machine on tho ground, even when there is :i fair wind

blowing, enabling tho pilot to run the machine close to the hangars or to other aircraft without the help of ground staff and with greater speed and accuracy. An additional advantage is the elimination of tho necessity for the use of chocks under tho wheels when running tho engine up prior to a flight. (b) Tho growing tendency for aircraft designers of tho larger machines to fit two, three, or four engines may bo mentioned here, for where more than one engine is fitted tho maehino can fly for the time being with one out of action, continuing until it reaches its destination or until a suitable landing ground is reached. Since the possibility or lire lias always to be reckoned with (petrol being the accepted present-day fuel for aircraft engines), devices such as fireproof bulkheads, non-return petrol valves, wing tanks, and fire extinguishers have been brought out with a view to minimising the danger. Tho possibility of an outbreak of fire has always to be reckoned with, ai:d therefore while safety devices such as those enumerated above will do much in their sphere to prevent accident or injury, true safety in this respect will only accrue from the installation of a power unit burning a much less inflamable fuel,' such, for example, as a development of the heavy-oil Dit-sel engine. (c) There arc many inventions in the nature of instruments iutended for tho use of the pilot of which want of space precludes mention of the majority, but the Schilovsky-Cooke turn indicator is worthy of note. It is an instrument designed to show when the machine is, off its normal straight course, and is composed of an electrically driven gyroscope rotating in a gimbal ring, the movement of the gimbal frame being indicated by a coloured transparent screen. Its sensitivity is such that it will indicate a turn at the rate of a complete circle in twenty minutes, and for'night flying, or flying in fog, enables the pilot to keep strictly on his course, any deviation therefrom being shown by a band of red or green light for a turn to port or starboard; tho wider tho band the quicker tho turn being made.

PARACHUTES.

(d) Parachutes are the most obvious emergency safety devices which have been evolved. They arc, of course, only for use in the last resort (since thpir adoption usually means tho abandoning of tho machine, which becomes useless after crashing), but they are of very real help and have already saved many lives. Two types —the Russell Lobe Parachute and the Irvino Parachute—have proved themselves perfectly efficient. Indeed, the Irvine is the standard parachute equipment of the British Eoyal Air Force.

The fitting of flotation gear, for uso whore an aeroplane may be forced to descend on water, emergency ripping panels for passenger aircraft to enable the occupants to get out more quickly than by the use of the door (which it may be impossible to open after an accident), emergency radio sets to keep in touch with rescue parties should the machine be forced down away from civilisation, and light rubber collapsible boats—all have added their quota to the safety of 'the occupants of aircraft in eases of emergency.