MultiEngine Study Guide

Piper Seminole
Vmc = 56 – never changes
Vmca – changes in flight – vmca in Seminole will always be lower than 56, unless the density altitude is really low.
Vmcg – minimum speed on the ground at which you can maintain directional control with the use of rudder alone. Larger planes do not use rudder to move nose wheel.

Factors that effect VMC
Story
Before you go flying calculate your most unfavorable weight and center of gravity. Before take off you set the flaps and trim for take off. Apply maximum available power. Put the gear up. Critical engine is lost. Propeller is wind milling. Apply no more than 5 degrees of bank. Apply 150lbs of rudder pressure. Climb out of ground effect.

1. Most unfavorable weight – light weight is most unfavorable because of the bank into the operating engine. A higher weight is favorable because the plane is creating more total lift and therefore more horizontal lift at the max 5 degrees, fighting the turning tendency. Higher weight decreases Vmc.

2. Most unfavorable Center of Gravity – Aft CG increases Vmc – shorter arm to the rudder, therefore it is less effective.


3. Flaps set for takeoff – airplane specific. Seminole flaps decrease vmca. Stabilizing effect . Increases lift and creates are greater lifting moment.

4. Trim set for takeoff – negligible.


5. Max available take off power. – Increases Vmc – more power, more yaw, more rudder.

6. Gear up – having GEAR DOWN decreases Vmc – keel effect, less rudder.


7. Critical engine lost – p-factor is greater, causing greater yawing tendencies. Increases Vmc.

8. Prop wind milling – More drag, more yaw , more rudder. Increases Vmc.


9. No more than 5 degrees of bank. – creating a horizontal lift component that counteracts the yaw. Less rudder is required. Decreases Vmc.

10. 150lbs of rudder pressure / Density altitude – higher density altitude decreases Vmc – less thrust is produced, less drag, less yaw, less rudder required.


11. Out of Ground effect. – decreases vmc.


Systems
Heater- Why do we want the whirling flame?
1. Stability – even heating of the canister
2. Efficiency.
What are the different blowers for?
1. Combustion – creates the whirling flame
2. Fresh air – cools heater and heats cabin. Nose gear switch turns of this blower.

Prop- below 950 rpm anti feathering pins fall in place.
Brings prop to Feather
1. Spring
2. Nitrogen Charge
3. Counter weights
Keep prop out of feather
1. oil pressure
2. Aerodynamic twisting force
How does the unfeathering accumulator work?

Holds high pressure oil from the governer. It is stored in the accumulator under pressure, until needed to move the prop back to normal pitch.

Electrical


Critical engine – the engine when lost that will most adversely effect performance. P-factor is the reason the engine is critical, it is the most pronounced.

Why is gear retraction low than gear extension?
Gear pump limitation – needs lots of pressure to bring gear up.

Supplemental Oxygen
Needed if above 12,500 for 30 mintues, crew needs it at 14,000. Passangers must
have it above 15,000.
a. Types
a. Continuous flow
b. Diluter Demand
c. Pressure demand

Pressurization
Isobaric control – maintains selected altitude.
Differential control – maintains set pressure differential between outside and
inside pressure