Summary of Types. To sum up the types required in military operations, we have: (1) High speed "Chaser" or "Scout" (Single seater), (2) High speed "Chaser" (Two-seat type), (3) Reconnaissance type, (4) Bombing type, (5) Gun or Battle Planes. This does not include the training machines of the two place and "Penguin" types, but as these are simply unarmed modifications of the two place reconnaissance and single seat machine, respectively, we will not go into further details at this point regarding their construction.
The Chaser or Pursuit Type. The most important factors in the design of a chaser are speed and maneuvering ability. The speed must be at a maximum in both the horizontal and vertical directions, for climbing ability is fully of as much importance as horizontal speed. Second in importance is the maximum altitude or "Height of ceiling" to which the machine can ascend. This maximum "Ceiling" generally goes hand in hand with the climbing speed, since a fast climber generally has a correspondingly high maximum altitude. The combination of weight and head resistance must be such that the climb interferes as little as possible with the forward velocity.
De Havilland. V. Single Seat "Chaser" or "Speed Scout" with a Single Rigidly Mounted Machine Gun on Top of Hood (To Left). It will Be Noted That the Top Wing is Staggered Back Instead of Forward as in the Usual Type, Thus Allowing the Pilot to Look Directly Up and in Front of the Top Wing. Dimensions Are in Millimeters.
Great climbing ability means a large power reserve, hence the weight carried per horsepower is reduced to from 8 to 12 pounds on the fastest machines, against the 16 to 18 pounds carried on the larger and slower reconnaissance types. Strength must be sacrificed to meet these conditions, so that instead of having a safety factor of from 8 to 12 as in the larger machines, it is cut to about 5.5, or in other words, the strength is relatively only half that of the usual type of aeroplane. This great reduction in strength calls for careful handling, especially in landing, and also painstaking care in the design and choice of materials.
High speeds and maneuvering ability both call for small wing areas and short spans, the areas being so adjusted that the resistance is at a minimum at the highest speeds. The short spans have a minimum of exposed interplane bracing and thus indirectly reduce both the head resistance and the weight. Unfortunately, the most favorable areas at high speeds are too small for safe landing speeds. With a fixed area, the minimum landing speed is only a little less than one-half of the maximum flying speed, hence with a maximum of 150 miles per hour the minimum will probably be little less than 70 miles per hour. The most efficient wing sections, and the greatest refinement in the body design, bracing, and chassis are necessary at speeds of over 100 miles per hour. All other conditions being equal, the resistance varies as the square of the velocity, hence at 150 miles per hour, the resistance is 2.25 times that at 100 miles per hour.
The following table gives approximately the apportionment of the head resistance producing items in a typical speed scout or chaser.
| Body (Fuselage) | 68 per cent |
| Chassis, wheels, struts, etc. | 15 per cent |
| Tail, rudder, fin, elevator | 5 per cent |
| Wing structure, struts, wire, fittings. | 12 per cent |
The aerodynamic drag due to the lift of the wings is not included in the above, the useless or parasitic resistance alone being considered. It will be noted that the body causes by far the greater part of the resistance, and as a result, the body of the speed scout requires the most careful attention in regard to streamline form. Fortunately this is possible with the short stumpy body of the chaser, since a true streamline form approximates the average body dimensions of the scout. In the larger machines, the body resistance is not as great in proportion to the other items since there are more struts and stay wires, the chassis is larger, and the tail surfaces are of greater area. The chassis is the next largest item and is one of the most difficult items to reduce. It has been suggested by several people that the chassis could be stored away in the body while in flight, but this adds additional mechanism and weight, and any automatic mechanism for folding up the chassis members would likely prove unreliable.