AN AEROPLANE STABILISER.

Press, Volume LXVIII, Issue 20488, 5 March 1932, Page 4

AN AEROPLANE STABILISER.

NEW ZEALANDER'S INVENTION. *

SATISFACTORY TESTS. S | i (from oub own correspondent.) LONDON, January 28.

Mr B. Roberts and Mr D. J. Young, of Auckland, arrived in London last September for the purpose of placing a patent on the market. Considerable secrecy was observed regarding their enterprise, doubtless for adequate reasons, but during the past week proper publicity has been given to a contrivance which experts state will make a great difference in the flying world. Matters have moved slowly but Mr Roberts and Mr Young now seem to have met with the success they deserve with what is known as the Roberts' Aeroplane Stabiliser. Official . experiments have been carried out with this ingenious contrivance, and it is understood that all who Jiave used the device in flying have expressed their approval of it. Among those who havo tried the device is Wing Commander K. R. Park (formerly of Dunedin), who found that it acted successfully, but as he was carrying out an official test he could not divulge his opinion. Further tests aro to be made by the exports at the Royal Air Force depot at Farnborough. It may also be mentioned that already Russian and Japanese firms have applied for information regarding the patent. In the current number of "Flight" there is an articlo on the new stabiliser. Tho writer says: Stabilisation or automatic control of aircraft is a subject which has exercised the minds of large numbers of designers and inventors ever since aircraft flew sufficiently to need controls at, all. So many patents have boen taken out covering various forms of automatic control that one could write a history on that subject alone. Such a state of affairs does not, however, mean that someone will not come along with a comparatively simplo idea which works far better than all tho previous inventions. Tho Stabiliser, or Control, which Mr Roberts has recently designed and fitted in a Moth, and which we describe hcte, is not yet perfect; in fact, it is certainly still in its experimental stage, but its promise is so great that it would bo idlo to imagine that it will not be further improved both in detail design and in its application. As at present fitted, it quite adequately maintains the Moth on an even keel laterally during straight flights or in gentle turns without there being the slightest necessity for the pilot to touch tho control column at all. This is just tlis same whether the weather is bumpy or not. Turns can also bo made solely by use of the rudder, provided this is used with discretion so that the rate of turn is such that the elevator is not really needed. Immediately rudder is applied the aircraft assumes its correct bank, and wo found that by easing the rudder slightly the turn could be maintained at a steady rate without losing height appreciridy. For faster turns it is necessary to alter tho tail-trim-ming gear, as this has the effect of applying more elevator. Unless this is done, of courso, the aircraft gradually, according to the amount! of rudder applied, drops its nose while the centrifugal force appears to increase the bank, thus bringing the aircraft into a steep diving turn

Acts Paster than Human Pilot. As already explained, in straight flight a bump causing a wing to drop is at once counteracted by the application of the correct aileron. This means that if, for example, the tailtrimming gear has been set so that the aircraft climbs steadily, climbs may be made through cloud with complete safety without touching the control column. It will naturally bo necessary to have a turn indicator as means of keeping a straight course, while the revolution counter and altimeter would be used all the time to check the fact that a steady climb was being maintained. Many other advantages have been claimed for this simple piece of apparatus by pilots who have flown it recently, but until we have tested it more fully we should hesitato to repeat that we have heard. A consensus opinion would, however, point to the fact that whatever the position of the aircraft may be, it will immediately) providing' tlie tail-trimming gear has been set correctly, assume normal flying position if the control column 13 let go free. In a spin it does not appear to make much difference, but j" coming out, all that' is required is to let go the column and. apply a little opposite rudder. "When nearly stalled, there appears far, less tendency to drop a wing than is normal with this type of aircraft, and this can only be accounted for by assuming that, the mechanism acts far faster and in a more correct manner than doeß any human pilot. . The invention is, of course, protecteu all over the world , and is being handled over here by Mr Roberts and o 3ir Young, working together as the koderts Aeroplane Stabiliser, Ltd., N ew Zealand House, 41$ Strand, London. Both these gentleman are New landers, and it speaks well for their patriotism that tliey should first ormg their remarkable invention to t" is country to develop. They are employing Mr Kay as their test pilot. Comments by. "Aeroplane." Tlio subject is also dealt with by tlio other important aviation journal, "Aeroplane." The writer, "F.D.8., says: —■ The other day at Heston we new a Moth equipped with a new device for automatic stability. It is the invention of Mr B. Roberts, of Auckland, New Zealand, who says that the idea first occurred to him while watching seagulls. Tlie way these birds used tlieir legs during manoeuvres suggested the application of a gravity system of automatic control. This fact will probably prepare students of aeronautical history—as it prepared us—for a device which is not precisely new in conception, fylany will remember the discussion and-dia-grams of a couple of decades ago, in which a downward prolongation of the control lever carried a weight, and the action of this weight was intended to maintain the aeroplane on an even keel. - These early devices wero condemned, if we remember rightly, on the assumption that automatic stability was not particularly desirable, and also because the effects of acceleration prevented the proper functioning of tho fore-and-aft control.'

Mr Roberts lias brought up the subject with refinements just at a tim® when automatic stability is being: sought. Blind flying is becoming popular, and the ordinary aerial tourist must be attracted by-anything which permits ot flying hands-off for indefinite periods, while navigation and otbw matters can be attended to with hands and eyes. The mechanical nature of : the automatic stabiliser is simplo in ' the extreme. The torque-rod which, inns foi-o-and-aft in thp control-box of the Moth has been replaced by. one with a loop fitting ;in th>> middle,': and; within the loop a vertical cylinder is suspended on aufiaitof trunnions, Xhe^qyJifldec

thus rocks laterally with the torquerod and its attached control-column. It also rocks fore and aft on the. trunnions and this movement is connected to that of the control-columns by a telescopic link which can be adjusted by a lever in the cockpit. In the cylinder is a second receptacle which contains 181b of mercury. The reason for having two is that the inner one can bo raised to the pivotal point by a cockpit control, and the device thus put completely out of action when not required. When it is in action the control-column is naturally heavier to operate, but all normal evolutions can be performed. Efficacy of Mercury.

The mercury does not quite fill its container, and this slight amount of freedom is said by Mr Roberts to add to its eflicacy. In discussing the stabiliser we suggested that an equivalent weight of something else might do equally well, but Air Roberts is convinced that the physical qualities of mercury are peculiarly important to the success of his invention. Candidly we remain unconvinced. Thereafter we tried the Moth, fitted with the Roberts stabiliser, after Mr C. E. Kay, who is doing the test work, had taken it up and demonstrated its hands-off capabilities. Personally we found an unusual sense of stability while flying with hands in pockets, and we circled for some minutes with constant changes of direction and rate of turn without once touching the stick. The rudder does not come under automatic control, but for touring purposes this is relatively unimportant besides being impossible to achieve by any gravity device. The pilot's hands are what he most needs for a great variety of purposes, and Mr Roberts's stabiliser does undoubtedly leave them free indefinitely, both on a straight course and when turning. Many aeroplanes fly hands-off in quiet air, but almost always with some slight feeling of precariousness which is quite absent with this device in action. If tho rudder be applied gently, the machine assumes correct bank without side-slipping. If the rudder be used roughly, the aeroplane skids as might i be expected, but takes up bank quite quickly. The main advantage may be taken to be that when the pilot wishes to consult maps or other things inside the cockpit, ho can quite safely retreat out of the draught and content himself with an occasional glance at the compass to correct his direction. The stabiliser will do the rest. Throughout all these manoeuvres the fore-and-aft control showed most need of further development. At certain engine revolutions and suitable settings of the telescopic link, straight flying could be maintained without variation in fore-and-aft level or speed, but in a turn tho nose first rose, then dropped and generally took a little time to straighten out. This is rather to be oxpected, we imagine, in view of the effects which acceleration has on pendulums. In assessing the efficiency of the stabiliser, the naturally good inherent stability of the Moth must be borne in mind. Tho absence of tail-trimming, on the other hand, is a point in favour of the new arrangement because the standard spring-loading used on the Moth had been taken off. /The machine came out of a spin with considerable promptitude when the stick was released, but inasmuch as we spun without any rudder on either side we are not prepared to say how much faster the recovery was than it would have been without the stabiliser. This is a test which comes rather outside the scope of a cruising stabiliser, and we have not even heard that fieorge the Robot has passed it with honours. The main thing is that Mr Roberts and his associates in the Roberts Automatic Stabiliser Co., Ltd., have apparently developed something which will free the pilot from a great deal of monotonous work which would otherwise keep hira from more important matters.