Twin Commanche


Study Guide


 
Systems and Limitations Overview

The following is an overview of the basic systems on the Twin Comanche. It is not intended to provide enough information for you to build the airplane. It is intended to provide general information for familiarization and review. For the latest and most accurate information, refer to the current AFM. Many flight manuals on older airplanes, if subjected to inspection, will be found to be out of date. Guess who gets the shaft if there is a problem, and you were operating with out of date information. Look in the nearest mirror and see!


Dimensions

Twin Commanche
Wing Span36'
Stabilator Span12' 6"
Gear Track9' 10"
Overall Length25' 2"
Wheelbase7' 4"
Turn Radius25' 6"
Prop Ground Clearance10"


Limitations
Weights
PA-30StandardTip Tank
Max Ramp 3,600 lbs3,725 lbs
Max Takeoff 3,600 lbs3,725 lbs
Max Landing 3,600 lbs3,600 lbs

Note: All weight in excess of 3,600 lbs must be fuel in the Tip Tanks.

Other than emergency, tip tanks must be empty for landing.

The above weights are maximum certificated limits. The actual safe maximum weights for a particular flight may vary due to the performance limitations. Although Normal Category airplanes are not specifically weight limited due to performance, you would have a very difficult time explaining why you were operating at a weight higher than your takeoff or landing performance would allow.

Unlike their Transport Category (FAR Part 25) big brothers, normal category (FAR Part 23 Twins), there is no requirement for Your Twin Comanche to be able to climb with an engine failure after takeoff. This being said, you can find yourself in a situation where you can't stop, and you can't go! I am not saying don't go to a high elevation airport and take off. Single engine airplanes do this all the time. I am saying BE AWARE of what single engine performance you should have, and plan accordingly regarding an engine failure during the initial climb after takeoff so you will know what to do in case it happens. For more information, see the "Jet Performance" section of this website.

For landing, I recommend that you determine the actual required landing distance according to the flight manual, then divide that number by 0.6 to give yourself a little margin. That's what the transport category aircraft do. The fact is that you can land an airplane places from which you do not have enough runway to take off ! The spirit of Charles Darwin is alive and well, and will not hesitate to intervene if you get stupid.


Speeds
Vne200 kts
Vno165 kts
Va141 kts
Vfe 109 kts
Vlo 130 kts
Vle 130 kts
Emergency Gear Extension87 kts
Vmc78 kts
Holding Speed
Recommended100 kts

Note: The "Recommended" holding speed is derived as follows. Vy = 97 kts. This will be very slightly above "Max Endurance" speed. The difference in fuel flow between these speed will be so slight it does not matter. It will also keep you from having to make as many power adjustments, as you won't be on the edge of being on the back side of the power curve. In this airplane, you will not have to worry about exceeding the maximum holding speed required by the FAR's. This would require the turbo model to be holding at max cruise, and that would be rather silly.

Recommended Minimum Maneuvering Speeds
ConfigurationRecommended / Minimum
Flaps Up90 kts
Flaps 15 deg85 kts
Flaps 25 deg80 kts

These speeds should keep you out of trouble if you keep the bank angle under 30 degrees.

Altitudes & Misc.
Max Alt T.O. & LDG (See Note) 10,000 ft
Max Altitude20,000 ft
Min Temp T.O. & LDG
Max Slush
Max Water
-40 Deg C
0.75 inch
0.50 inch
Max Temperature
Abv 10,000 ft
ISA + 35 C
ISA +30 C
Min Temp SL - 3,500-40 C
3,500 - 5000 Linear-40 C to -35 C
5,000 - 10,000-35 C
10,000 - 35,000 Linear-35 C to -70 C
Above 35,000-70 C
Max Demonstrated X-Wind20 kts
Max Runway Slope2%
Max Tailwind Component T.O. & LDG10 kts
Load Factor Limit
Flaps Up
Flaps Extended

3.8 G
2.0 G

Note: Regarding the altitude for takeoff and landing, the performance charts only address altitudes up to 8,000 MSL. Extrapolation of these charts is invalid. Although you are not specifically limited, you have no performance data for the airplane. This being said, if you take off above an altitude or temperature where published data exists for the airplane, you are now a test pilot. I am not saying that if you take off from Telluride, elevation 9,078, or Leadville, elevation 9,927 that you are going to die. Just be way on the careful side until you have the experience to know what your airplane will do when you are "Off the Charts" from a performance standpoint. An old rule of thumb states that compared to sea level, takeoff distance is double at 5000 feet, and triple at 8,000 feet. I would guess takeoff distance at 10,000 feet might be quadruple the sea level distance, but that is only a guess on my part. BE AWARE !

Lycoming IO-320-B1A Engines
MPRPM
Takeoff Max2700
Max ContinuousMax2700
Recommended Climb25"2500
Rec Max Cruise Max *2400
Ground Idle -------1000

Note: Full throttle at 8,000 MSL is 75% power. If cruising below 8,000 MSL, adjust the MP accordingly.

Max Oil Temp+245 F
Min Oil Temp for Start
Pre Heat if Colder
-40 C

Flight Controls

The flight controls on the Twin Comanche are cable driven. Other than physical inputs from the pilot, the Autopilot is the only thing that will move the flight controls ailerons, elevator and rudder. The flaps are electric.

Ailerons

The Ailerons on the Twin Comanche are cable driven. Optional aileron trim is available but was not installed on the airplane at the factory. N8701Y is not equipped with aileron trim.

Stabilator

The Twin Comanche is equipped with a moveable Stabilator. The Stabilator is also referred to as a "Flying Tail". When you move the control wheel forward or aft, the angle of incidence of the entire horizontal tail. Is it better than the standard fixed horizontal stab and moveable elevator? Piper thinks so, as well as Lockheed (F-104 L-1011 & F-22) and the fine folks who built the F-4 Phantom and the builders of the F-8 Crusader. These folks had a better idea. Pitch trim is provided by cockpit adjustable "Anti-Servo Tab" mounted on the trailing edge of the Stabilator. This tab also increases the force required to deflect the Stabilator as pitch control inputs are applied farther from neutral and at higher speeds.

Rudder

The rudder, like the rest of the flight controls the rudder is operated manually. Rudder trim is available using a trim know just below the throttle quadrant.

Flaps

The flap system is electric. Flaps may be extended to 15 deg, and 25 deg. Flap Gauge

Max Flap Extension Speeds
15 deg109 kts
25 deg109 kts

Brakes

The normal braking system provides braking to all of the main gear wheels. The main wheel Autopilot

Autopilot - Altimatic III-B Autopilot

Autopilot Limitations
Altimatic IIIB Autopilot:
Above Vmo/Mmo
Below 1.2 Vs
With Electric Pitch Trim Inop
During coupled approaches with an engine inop
During takeoff or landing
Engines

The standard Twin Comanche are equipped with two Lycoming IO-320-B1A 160 HP engines. The IO stands for Injected Opposed. The 320 is the displacement in cubic inches. B1A is the particular mode of the IO-320 engine. On the Twin Comanche's with counter rotating propellers, the right engine will be an "LIO-320. The "L" means it rotates to the left. This requires a different crankshaft, camshaft, and accessory case among other things.

Engine Gauges

Engine Start Panel

Electrical

The Twin Comanche is equipped with two alternators, or as on the earlier models, two generators.

Hydraulic

The only hydraulics on the Twin Comanche are used to operate the brakes. A brake fluid reservoir is located in the nose compartment. Each brake master cylinder receives fluid from the brake reservoir through its own supply line from the reservoir itself. Each brake master cylinder provides hydraulic pressure to its respective brake caliper through its own hydraulic line between each brake master cylinder and its respective brake. There no power brakes or anti skid system installed on this airplane.


Fuel System

The Twin Comanche Fuel System is simple. Fuel is stored in the wings. The standard airplane has 4 fuel tanks. The Main Tanks (Inboard) hold 30 gal each. The Aux Tanks (Outboard) each hold 15 gal. Tip tanks holding 15 gal each were an option.

There are many optional fuel tank STC's for the Twin Comanche. A baggage compartment 20 gal tank is approved. Nacelle tanks can be installed with ether 10 or 20 gal per side.

FuelMain Tanks
Each
Aux Tanks
Tip Tanks
Each
Total
Standard30 gal15 galN/A90 gal 540 lbs
Tip Tank30 gal15 gal15 gal120 gal 720 lbs
Fuel System Switches


Electrical System

Altitudes & Misc.
Alternators 60 Amps
Battery12 Volt / 36 Amp Hour

Ice and Rain Protection

Note: Twin Comanche N8701Y, PA-30-160 SN # 1849 is not certified for flight into known or forecast icing conditions.

Engines

Wings & Tail

The Twin Comanche may be equipped with optional Wiggins Airways wing and tail de-ice boots.

Not installed N8701Y PA-30-160 SN #1849

Windshield

The pilots windshield can be equipped with an optional external electrically heated pane for those aircraft with the anti-ice system installed.

Not installed N8701Y PA-30-160 SN #1849

Propeller Anti-Ice

The optional Wiggins Airways alcohol propeller anti-ice system may be installed.

Not installed N8701Y PA-30-160 SN #1849

Pitot Heat

The pitot tube on the Twin Comanche is electrically heated.


Environmental

Heater


Warning Lights