(continuing post)
Take off is made with 1 degree nose up tailplane trim, 20 degrees of flap lowered and always with the tailwheel locked. After lining up the throttle is smoothly opened to 1.1 ata, controlling the moderate left swing with rudder. Once the take-off power is set and the aircraft is directionally under control, the tail is gently raised just clear of the ground. The aircraft lifts off at around 150 kph with slight back pressure on the stick. This may sound simple, but is one of the most difficult tasks in flying the '109. If any swing is allowed to develop the toe-in on the outside wheel turns the aircraft even more i.e. it is directionally unstable. It will then roll about the outside wheel, leading to the classic ground loop. This problem is accentuated because the forward field of view is so poor that it is difficult to detect any swing starting. The only saving grace is that the lockable tailwheel gives some directional stability, and so it is kept on the ground for as long as possible. The gyroscopic effect of the propeller and loss of directional stability from the tailwheel once the tail is raised is marked, hence the tail is raised very gently and only slightly.
Once airborne, engine handling is markedly different from similar British and American engines, due to the lack of a constant speed unit on the propeller. The operating philosophy is that the engine has a running line of optimum rpm for a given manifold pressure; 2000 rpm at 1.0 ata, 2300 rpm at 1.15 ata (max. continuous) and 2600 rpm at 1.3 ata (30 minute limit). These rpm are also the minimum for the manifold pressure without overboosting the engine. The pilot sets the manifold pressure with the throttle, and engine rpm is controlled either automatically (when it is governed to the running line) or manually. Manual control is by a rocker switch on the throttle and this varies the propeller blade pitch. Once set, the propeller runs with fixed pitch, RPM increasing with increasing airspeed and vice versa. Cockpit of blade pitch is on a clock. For example, 12:00 is set for take-off and 11:45 for landing. Initially, we always flew the aircraft with manual RPM control, until we were happy with the automatic control functioning. In a display, 1.15 ata is set and RPM controlled manually to 2400-2500 to prevent overboosting. This requires a setting of around 11:05 at high speeds such as for loop entries, and an increase to around 11:20 over the top of a loop. This results in a lot of head-in-cockpit time and propeller adjustment during a display, greatly increasing the workload.
The Bf109G is heavy to manoeuvre in pitch, being similar to a Mustang. At 520kph it is possible to pull 4g with one hand, but I find it more comfortable to use both hands on the stick for looping manoeuvres, normally entered at 420kph and 3g. Pitch trim changes with speed are moderate, and the tail plane trim wheel mounted abeam the pilots' left hip is easy to use. For a display, I run it at 420-450kph in trim, and then do not retrim. This causes no excessive stick forces during the display. Overall the aircraft is straightforward to handle in pitch.
Roll performance is similar to a Hurricane or elliptical wing tipped Spitfire. A full stick roll through 360 degrees at 460kph takes 4 to 4.5 seconds without using rudder, and needs a force of around 20 lbf. One interesting characteristic is that rolls at lower speeds entered at less than 1g, such as a roll-off-the-top or half Cuban, have a markedly lower roll rate to the right than to the left. Therefore, I always roll left in such manoeuvres.
There are two problem areas in yaw control with the '109. Firstly, directional stability is low and marked slip ball excursions occur with any changes of speed or power. Also, there is moderate adverse aileron yaw (right yaw when left aileron is applied, and vice versa). The rudder force to centralise the slip ball is low, but constant rudder inputs are required during manoeuvres to minimise sideslip. If the slip ball is not kept central, the lateral force on the pilot is not uncomfortable and no handling problems occur, but it looks very untidy in a display. At the top of a left wing-over, you are very cross-controlled, with left aileron and lots of right rudder applied. This lack of directional stability makes it hard work to fly the aircraft accurately and neatly, although there are no safety problems. However, it must have made accurate tracking for a guns 'kill' very difficult. I suspect that many '109 kills were made at very close range! It also says a great deal about the shooting skills of the Luftwaffe Aces. The second problem is the lack of a cockpit adjustable rudder trimmer. The fixed tab is set so that the rudder is in trim during the cruise, reducing footloads during long transits. However, for all other airspeed and power combinations, a rudder force must be applied. This is an annoying feature, and I am surprised that a rudder trim tab was never fitted to later models such as the Gustav.
The idle power stall characteristics of the aircraft are very benign and affected little by undercarriage and flap position. Stalling warning is a slight wing rock with the stick floating right by about 2 inches. This occurs 10klph before the stall. The stall itself is a left wing drop through about 15 degrees with a slight nose drop, accompanied by a light buffet. All controls are effective up to the stall, and recovery is instant on moving the stick forward. Stall speeds are 155kph clean and 140kph with gear and flap down. In a turn at 280kphwith display power set, stall warning is given by light buffet at 3g, and the stall occurs at 3.5g with the inside wing dropping. Again, recovery is instant on easing the stick forward. One interesting feature is the leading edge slats. When these deploy at low speeds or in a turn, a 'clunk' can be heard and felt, but there is no disturbance to the aircraft about any axis. I understand that the Bf109E rolled violently as the slats deployed, and I am curious to know the difference to the Gustav that caused this.
Back in the circuit, the '109 is straightforward to fly, except that it takes around 25 secs to lower the flaps, using a large wheel mounted next to the tail plane trim wheel and on the same shaft. A curving final approach is flown at 200kph, and once aligned with the runway the forward field of view is poor. The threshold is crossed at 175kph, the throttle closed, and the aircraft flared to the 3 point attitude. The '109 floats like a Spitfire and controls are effective up to touchdown. After touchdown, directional control is by using differential braking. The three point attitude is easy to judge, and although it bucks around on rough grass it does not bounce significantly on touchdown. however, the landing is not easy. From approaching the threshold up to touchdown the forward view is very poor, and it is difficult to assess drift. if the aircraft is drifting at touchdown, the toe-in on the wheel towards which it is drifting causes a marked swing, and you are working very hard to keep straight and avoid a ground loop. Each landing is a challenge, and just a bit unpredictable. Hard runways have higher friction than grass surfaces, and so the wheels dig in even more if drifting on touchdown, making ground-loops more likely on runways than on grass. The possibility of drifting on touchdown increases with a crosswind, and so for these two reasons, we are only flying the Gustav off grass and with a 10kt crosswind limit.
<<<<
I realize that when simulating an aircraft, it is obviously not possible to have all characteristics replicated that a real aircraft might display. My question is not intended as a criticism, or a demand, I am just wondering how complex you intend to be.
Thanks for all your hard work on IL-2 and Battle of Britain. We are all looking forward to your next publication.
