Flight, January 1937

ECONOMICAL TRANSPORT for TWO
Flying the Porterfield "70": A Tandem-seater Cabin Monoplane Which Cruises at 100 m.p.h. on 70 h.p.

   DESPITE the increasing popularity of side-by-side seating for both luxury touring and training, the tandem arrangement still has a very great deal to recommend it. Apart altogether from the desirability of complete control freedom, the lone pilot can be provided with a "both sides" view which is very pleasant and useful near a crowded aerodrome or when flying in bad weather.
   In the American Porterfield monoplane, the agency for which, in Western Europe, has recently been acquired by Sumy Flying Services, the seats are arranged in tandem and, more important, the machine may be flown solo from either - suggesting that, as a stepping stone from a standard trainer to a cabin machine, it might lie very useful. The view from the front seat (the only one I tried) is fair to good, though, until one has spent several hours in a particular machine, judgment on this point is somewhat premature. During a turn a high wing comes down to cover that part of the earth which, especially during an approach to land, the pilot most ardently desires to see; in the Porterfield it is possible to put one's head, so to speak inside the deeply curved screen and to see what would otherwise be cut off.

Essential View

   With such an expanse of deep window in a high-wing monoplane the view of the ground in level flight is everything that one would expect. In cruising attitude the top of the engine cowling lies decently below the level of the horizon and only while taxying does the nose impede vision - a fault to which all single-engined machines are prone. The left-hand windows may be opened for ventilation or for landing in rain.
   So much for the view question, which I consider to be most important when dealing with a machine designed primarily for the amateur pilot. The second most important concerns maintenance costs. Welded steel tube fuselages are not very common in this country, but, short of making a landing which would crack a couple of longerons in a wooden machine, it is difficult to see what could go wrong. The wing is of straightforward wooden construction, with steel bracing struts, and the Le Blond radial has a successful six years' reputation behind it. The control cables can be readily inspected and the entire machine has an air of rugged simplicity
   As a flying machine the Porterfield, though small and light, is still typically American, with a light rudder and somewhat heavy ailerons. Much of this apparent heaviness is caused by stiffness in the control operation itself, and the ailerons are certainly effective right down to the stall. In any case, the machine is virtually without vice and sits about the sky at all speeds as if hung from a cord. Let everything go in a tight turn and it yaws its way back to level; hold the stick right back and the machine merely wallows momentarily before dropping its nose and repeating the process. A steep sideslip can be held, using full rudder, without an increase in speed, though a crab sideslip provides the most effective method of losing height. The landing process, with a somewhat heavy elevator movement, should be almost foolproof.
   The only control criticism worth mentioning concerns the position of the trimming lever, which is arranged on the left side behind the front seat so that it can be used by either occupant. Its somewhat awkward placing would be of small account if it did not, in addition, require an excessive number of turns - though the machine, even when flown from the front, can be held up comfortably in the glide without alteration of trim. The heel brake pedals, which are duplicated, are easily used with accuracy after a little practice.
   Since neither the A.S.I, nor the altimeter were working properly at the time of the trial, no first-hand performance figures can be given, but the take-off run given in the table is certainly not optimistic. I flew the Porterfield both solo and otherwise, and in a moderate breeze the machine was comfortably air-borne in rather less than a hundred yards, provided that it was pulled off the ground.
   The price includes all the usual instruments, including a compass, and navigation lights and battery can be fitted for ?10 if ordered with the machine. Accommodation for luggage is provided in a locker at the rear of the cabin.
H. A. T.

THE PORTERFIELD "70"
70 h.p. Five-cylinder Le Blond

   Weight loaded 1,310 lb.
   Weight empty 800 lb.
   Maximum speed 115 m.p.h.
   Cruising speed 100 m.p.h.
   Landing speed 40 m.p.h.
   Range 350 miles.
   Rate of climb (full load) 600ft./min.
   Take-off run (full load) 130 yards
   Landing run 130 yards
   Price ?635
   Distributors Surrey Flying Services, Ltd., Airport of London, Croydon, Surrey.