These notes are for the information of Lasham Tug Pilots and give Lasham operating procedures with the aircraft type. They do not supersede the information in the Aircrew Manual for the type, a copy of which is held in the office and should be consulted from time to time as appropriate.
4.13 THE SUPER CUB. The Piper Aircraft 18 (PA 18) Super Cub first appeared in
1949 and is descended from the original J3 Cub and the PA 11 Cub Special. The
Super Cub continued in production until 1969 and over 10,000 were made fitted
with six different size engines between 95 and 150 hp. During 1989 the new
Piper Aircraft Company started making Super Cubs again. Apart from the basic 95
hp version which did not have flaps or counterbalanced elevators, all the
airframes were similar with flaps as an option. Super Cubs also joined various
Air Forces as L18s (95hp) and L21s (125hp), some people incorrectly call these
PA 19s once they have been civilianised but this series number was never used by
Piper. By the mid 1960s, the price of secondhand Super Cubs had fallen
sufficiently for the growing gliding movement to operate them and the advantages
of the Lycoming 150 engine, performance, economy and reliability, soon became
apparent.
G-ATRG. Lasham bought G-ATRG in 1966 for 1750. It was built in the mid fifties
and was converted by Pipers in 1962 to a crop sprayer. It was then shipped to
England, and then on to Cyprus where it was registered as SB-CAB. Finally, in
1966 it was re-registered in the UK and the spray gear removed. It is an old
aeroplane, and needs handling as such.
Modifications Made to G-ATRG. We have done 3 significant modifications. The
first was to change the cockpit glazing in 1977 to the military style with
improved view. Cleveland disc brakes came next, and finally the 150 hp engine
was replaced by a 180 hp unit. The only snag was the fuel system, which despite
fitting larger bore fuel pipes, was just unable to meet the official
requirements for fuel flow with the more powerful engine from the lower part of
the left tank and all of the right. For this reason the tanks have been
placarded as the left tank being the Main Tank with 7.5 gallons of its 15 gallon
capacity being officially available only for cruising flight, and the right tank
is now named the Auxiliary Tank and has 15 gallons available for the cruise. In
practise we have found no fuel flow problems, and the official requirement which
was tested on the ground was for a fuel flow in excess of that actually demanded
by the engine at full power, because the CAA impose a proof factor of 1.5 as a
margin. Finally, the fabric has been re-covered twice by Lasham, the last time
during the winter of 87/88 quite a bit of structural repair was done at the same
time resulting in a total overhaul cost of 7000.
Flaps. Super Cubs have two stage flaps, 25 and 50 degrees. The flap limiting
speed is low at 85 mph (74 Kts) and there are significant trim changes with the
use of flap. Roll response to aileron is reduced with flap, so in turbulent
conditions, land with half or no flap.
Weights. The Max AUW is 1750 lbs and TRG weighs 1122 lbs dry, giving a total
disposable load of 628 lbs. Full fuel (30 gal) weighs 216 lbs giving you a
possible cockpit load of 412 lbs, but note that only 50 lbs can go behind the
rear seat before you exceed the aft C of G limit. Normally we only put the
spare rope and the detachable rear stick in the stowage behind the rear seat.
Stalling. In flight the aircraft has reasonable but not sprightly handling, and
has a docile but positive stall. However, at least one Super Cub, not ours, has
been spun in from a low steep turn so do not expect the aircraft to correct your
mistakes! Remember that the most docile characteristics shown in smooth air may
prove very different in conditions of turbulence and wind gradient ! If in
doubt about stalling characteristics when you are flying a tug, stall it gently
at a safe height, such as during a return from a tow. But bear in mind that
later near the ground you have wind gradient, turbulence, and other control
movements to contend with, all of which need a good increment over the stall to
ensure safety. And if you fly it on another day, the stalling speeds may not be
the same because ASIs are sometimes changed, ASI tubing can develop kinks, bugs
or grit, and both speeds and characteristics will be different if the wing
surface has mud on it, is wet, or a repair on the leading edge has been made.
Poor View into Turns. As with most high wing aircraft, view into a turn is poor, so
develop the habit of lifting the inside wing first for a lookout prior to turning.
Trimming System. The trim system uses a screw jack to move the leading edge of
the tailplane. This provides a powerful trimmer but requires no less than 26
turns of the cockpit handle to cover its full range. It is therefore not easy
to retrim quickly if you take off with the trim significantly out of position
and the stick loads are high so be sure to set it before each flight. Note that
pilots with long arms can knock the rear throttle with their elbow when
retrimming.
Wheel Brakes. Cubs have heel brakes providing independent braking to each
mainwheel. The brakes are usually quite powerful and if too much pressure is
used on them the aircraft can easily be nosed over. A parking brake function is
provided by the small lever on each of the two the brake cylinders under the
front seat being pulled back while the heel brakes are pushed; a further firm
push on the heel brakes then releases the parking brake.
Flying with the Doors Open. The aircraft can be flown with the doors open
provided they are securely tied, but there is a considerable performance loss in
this condition. This should only be done for a specific purpose such as
approved air-to-air photography.
Crosswinds. Super Cubs have a Flight Manual crosswind limit of 12 mph (10.4
kts), but they are reasonably easy to handle in crosswind take offs because, due
to the high wing, they can either be carefully banked onto the upwind wheel in
the final part of the ground roll, or held down with forward stick and then
cleanly unstuck at a slightly higher speed than usual. Crosswind landings are
less straightforward. In crosswinds approaching the limit, wheeler or
`tail-down wheeler' landings using half or no flap are best, using an initial
approach of 70 mph, reducing to a slightly higher Threshold Speed than normal,
checking slightly forward with the stick on touchdown (to keep the main wheels
firmly on the ground) and initially keeping straight by gentle differential
brake, until the tailwheel is firmly on the ground as speed falls and you get
directional control from the tailwheel. This is also a good technique if
landing on tarmac, particularly in any crosswind, since tailwheel aircraft are
particularly directionally unstable on hard surfaces (more stable on longish
grass) and three-pointing can more easily lead to ground looping.
Strong Winds. Light tailwheel aircraft cannot be operated safely in wind
conditions that are OK for heavier low wing nosewheel aircraft; so choosing the
time to put the Cub away if the wind is getting stronger is a critical one and
safety must be the overriding factor. 20 knots or gusty/turbulent conditions
are limiting for Cubs. If, as you taxy down wind, the flaps blow down despite
their springs, then the wind is too strong for a Super Cub.
General. These notes are not intended to teach you how to fly taildraggers. We are
prepared to do tailwheel conversions for those with only tricycle experience but pilots
in this situation should first read some of the books written on the subject to get an
understanding of the likely problems. A discussion of topics such as ground-loops,
nosing over, handling bounced landings etc will precede the flying.
THE DI, COVERING ONLY POINTS PARTICULAR TO THE SUPER CUB
Include the other normal DI checks as you go around the aircraft.
TAXYING. Remember that tailwheel aircraft are basically directionally unstable on the
ground and so can be ground-looped if your attention wanders or you try to turn too
fast. Use full back stick for taxying to keep a good pressure on the steerable tailwheel,
unless going downwind in a strong tailwind in which case keep the stick central.
Always use rudder first for steering assisted with brakes when absolutely necessary.
ENGINE FAILURE `Fly the aircraft' as a first priority so that you do not, for instance,
stall, or lose reference on a landing field. Only then, diagnose the fault and attempt
remedial action.
LOWER THE NOSE
Check:
When committed to engine-off landing;
CONDITIONS: MEDIUM LENGTH GRASS (Unstick Dist increased by 25%)
Tug AUW 1400 lb, 20°C, no wind, no slope, 600 ft pressure height
CRUISE: Depending on conditions, fuel consumption is between 7 and 12 imp gal
per hour, endurance on full fuel between 3-4.5 hours and range 250 - 320 NMl.
For more exact figures, consult the flight manual. Towing a draggy glider will
degrade these figures considerably although modern glass gliders have very
little drag, and towing a heavy glider will cause substantially more fuel to be
used in any climb.
LANDING Conditions: 1400 lb AUW, 20°C, no wind, no slope, pressure height 600
ft, runway or short grass
Last updated by John Leibacher on Sunday, November 5, 1995 at 17:47
>
SUPER CUB - CHECKS
START UP
RADIO................ OFF
MASTER SWITCH ON
FUEL................. SELECT TANK
MIXTURE.............. RICH (In)
BRAKES............... ON or at least feet on heel brakes
THROTTLE SET (1/2 inch open)
STICK BACK
MAGS LEFT MAG ON
*START*, then check
OIL PRESSURE.... Rising
RIGHT MAG......... ON
AMMETER......... CHARGING
RADIO............. ON
RUN UP AT 1800 RPM. MAX MAG DROP 125 RPM. Avoid prolonged
ground runs to prevent hot spots damaging cylinders. Typical carb heat drop 100 rpm.
PRE TAKE OFF CHECKS - SUPER CUB
Mnemonic: T MM FF I HH C
Trim..................... HALF (about 12 turns from full in either direction)
Mixture.................. RICH, knob fully in
CARB HEAT COLD
Mags..................... BOTH ON
Fuel..................... CORRECT TANK, CONTENTS
Flaps.................... UP
Instruments.............. NORMAL
Hatches.................. CLOSED & LOCKED
Harness.................. TIGHT & LOCKED
Controls................. FULL & FREE
TOWING SPEEDS mph (Kts) - SUPER CUB, NO FLAP
MINIMUM TOWING SPEED..... 50 mph (43 Kts)
K13.................... 60 mph (52 Kts)
Normal GLASS GLIDERS....... 70 mph (60 Kts)
WATER....... add 6 mph (5 Kts)
ENGINE FAILURE - SUPER CUB
GET RID OF GLIDER
BEST GLIDE SPEED
FOR RANGE IN NIL WIND: 58 MPH (50 Kts), about 1:8 prop stopped, 1:7.5 prop rotating
SELECT FIELD, TURN IF NECESSARY
R/T - MAYDAY TO LASHAM WITH POSITION & LIKELY LANDING AREA
FUEL CONTENTS & TANK SWITCH, SWITCH TANKS ANYWAY
MIXTURE LEVER - CHECK FULLY RICH
MAGS - TRY SWITCHING TO A SINGLE MAG
THROTTLE - EXERCISE TO TRY AND GET A RESPONSE
MAGS - OFF
FUEL - OFF
STRAPS - TIGHT
DESCENT - SUPER CUB
ROUGH AIR SPEED (Vra) 121 mph (105 Kts)
MAX MANOEUVRING SPEED (Vm) 94 mph (82 Kts).
Above this speed the aircraft
is only cleared for use of one third of the available control surface deflection. This may
not be enough for emergency collision avoidance action.
APPROACH
FLAP LIMITING SPEED 85 mph (74 Kts)
INITIAL APPROACH
Strong Winds 70 mph (60 Kts)
Slack Winds 60 mph (52 Kts)
MIN THRESHOLD - FULL FLAP
Vref, speed for round-out 50 mph (43 Kts)
SHUT DOWN
RADIO OFF
Mags Dead Cut check at Idle
MIXTURE FULLY LEAN.
Engine Stopped
MAGS OFF
MASTER SWITCH OFF
BRAKES A/R
PERFORMANCE DATA - SUPER CUB
Tables are given in the Flight Manual for Takeoff, Climb, Cruise and Landing.
Because of the different prop on Lasham aircraft, our performance will be
somewhat different, as well as the longer takeoff and slower climb due to towing
gliders of differing weights and drag. It is intended to take measurements at
Lasham with a video camera of takeoffs (with and without gliders) and landings,
and produce some revised figures specifically for our aircraft later. Meanwhile
some figures derived from the Flight Manual are shown below; use with caution
until validated by measurements on G-ATRG:
TAKEOFF:
CONDITIONS: Runway, tug AUW 1400 lb, 20°C, no wind, no slope, 600 ft pressure
height
AUW of glider, lb: 500 600 700 800 900
Unstick Dist, ft 618 657 703 782 841
Dist unstick to 50 ft 505 582 676 815 948
Total dist to 50 ft 1123 1239 1379 1597 1789
CONDITIONS: SHORT GRASS (Unstick dist increased by 10%)
Tug AUW 1400 lb, 20°C, no wind, no slope, 600 ft pressure height
AUW of glider, lb: 500 600 700 800 900
Unstick Dist, ft 680 723 773 860 925
Dist unstick to 50 ft 505 582 676 815 948
Total dist to 50 ft 1185 1305 1469 1675 1873
AUW of glider, lb: 500 600 700 800 900
Unstick Dist, ft 772 821 879 977 1051
Dist unstick to 50 ft 505 582 676 815 948
Total dist to 50 ft 1277 1403 1555 1792 1999
Distance from 15m / 50 ft = 911 ft
50 ft to touchdown = 569 ft
Landing Roll = 342 ft
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| Dr. Günther Eichhorn | Springer 233 Spring Street New York, NY 10013 USA, email me |