Chapter 2 Aircraft Performance - Rans S-12 Airaile Pilot Operating Handbook

Chapter 2 Aircraft Performance

Overview
Comprehensive performance charts (takeoff distances, rate of climb, etc.) are difficult to devel-
op in 40 hours of flight testing. It is generally not possible within the scope of basic flight test-
ing to experience the meteorological conditions that would allow a test pilot to generate data
for all density altitudes. This factor and the general performance of this aircraft lend them-
selves to one important performance characteristic: log time in the airplane and learn for your-
self the maximum performance characteristics if you need to push the envelope. Suggestions
of climb performance and take-off and landing distances charted at the end of this chapter are
logical estimations given by the test pilot.
Operational Milestones
This aircraft has been flown to 14,000 feet MSL with a single pilot, it has been operated on
very short (300 feet), very rough fields (furrowed field), it has flown in 20 to 25 mph winds,
it has flown in formation with other aircraft, and it has been flown at gross weight of 1100lbs.
Maximum demonstrated crosswind by the test pilot during the certification phase was about 10
knots.
Typical Engine Performance
As for engine performance, it is best to review the Rotax operating manual. This manual does
a very good job of informing the pilot with respect to engine performance and engine operating
parameters. As a fundamental means to knowing engine limitations, the following apply and
were observed during the first 40 hour test period:
RPM: Maximum 5 minutes at full throttle, Maximum 5500 continuous
Oil Temp: Do not takeoff less than 130 F or operate higher than 270 F
Oil Pressure: Typically comes up to 65psi immediately and stays there
CHT: Should be at least 130 F for engine runup and typically below 200 F
Water Temp: Raises to 130 F for runup and typically below 200 F
Water Pressure: Increases to 12 psi and may drop below that in cruise
Fuel Burn: Calculate flight plans with 4.5gph fuel usage and 65mph cruise
An important consideration for engine performance figures is a result of the very effective
cooling system of this aircraft. In cold weather it becomes necessary to block off the air inlet
to the radiator to keep the engine temperatures in the green. If you notice unusually cool
engine operation in flight, the best thing to do is descend to a lower (and warmer) altitude and
land when convenient to cover up the radiator inlet.
Takeoff and Landing Distance
In most any case, the runways typically encountered at modern day airports will be far longer
than necessary for the S-12, even on a warm day at gross weight. However, the novice pilot
should not attempt to operate on low performance days near gross weight with less than 1000
feet of runway. This is a scenario reserved for the pilot who is familiar with the aircraft. If
flying solo and reasonably familiar with the airplane, 500 feet of runway (without obstacles)
will usually suffice. With 50 foot obstacles in the same conditions, for takeoff or landing, a
good pilot should give himself 750 feet of runway. If all conditions are in the pilots favor
(pilot skill, sea level, 15mph headwind, solo pilot, smooth runway, no obstacles) then 200 feet
of runway can suffice for takeoff and 300 feet for landing. The main reason for increased
landing distance is the lack of braking power.
Figure 2.1 - Take-off and Landing Distance Chart
This take-off/landing distance chart is to be used as a guide for the new pilot. All of these
distances are purely estimation (extrapolated from key data points gathered during the testing
phase) by the test pilot and should serve as a general reference only. As a pilot of this aircraft,
you should be experienced in the plane before trying to fly yourself and a friend into a remote
area at high altitudes for an afternoon of hiking. You may find youself commited to an impos-
Density Altitude Take-off Weight (lb)
0 820
5000 820
10,000 820
0 1100
5000 1100
10,000 1100
0 820
5000 820
10,000 820
0 1100
5000 1100
10,000 1100
For any given condition: allow 10 percent runway distance increase per 1000' density altitude chage; allow 40 percent runway
increase from smooth to rough conditions; allow 30 percent runway increase from minimum weight to gross weight; allow 8
feet per foot obstacle clearance; allow 2 percent runway distance decrease per knot headwind.
sible landing with not enough performance to execute a go around.
Best Glide and Rate of Climb
As previously mentioned, this data was collected for one set of conditions only and best esti-
mations must be used to extract the data to meaningful numbers at different weights and alti-
tudes. This rate of climb data was collected at a take-off weight of 880lbs at an elevation of
4000MSL with an ambient air temperature of about 55 to 60 degrees fahrenheit.
As density altitude increases, two factors change the performance characteristics of the aircraft
with regard to climb rate:
Engine power output decreases as altitude increases
Propellor effeciency decreases as altitude increases
It is important to understand that both of these effects are additive and will reduce performance
to a sub-par level at high altitudes. While testing the service ceiling at around 820 pounds,
6167U was observed to have a 200fpm maximum climb rate at 14,000 indicated altitude. At
gross weight and 10,000 density altitude, you may find yourself unable to attain more than a
200 fpm climb.
Figure 2.2 - Power On Rate of Climb Chart
The conclusions reached from the power on rate of climb test data are:
1) Best available rate of climb: no flaps, 50mph IAS, 760fpm
2) Best available angle of climb, 3 notches, 35mph IAS, 650fpm
3) Safest climb (test pilot's recommendation: no flaps, 65mph, 700fpm
Although the true best angle of climb is obtained with full flaps at 35mph indicated, this is not
the safest procedure to follow because it is right at the stall speed of the aircraft and engine
failure would be difficult to recover from. Only hours of practice and experience will allow
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Obstacle Clearance (ft) Surface Condition Runway Length (ft)
0 Asphalt
0 Asphalt
0 Asphalt
0 Asphalt
0 Asphalt
0 Asphalt
50 Grass/Dirt
50 Grass/Dirt
50 Grass/Dirt
50 Grass/Dirt
50 Grass/Dirt
50 Grass/Dirt
500
700
1500
650
1000
1900
700
1000
2200
900
1300
2600