1
Q
Max Ramp Weight
A
3816 lbs
2
Q
Max Takeoff Weight
A
3800 lbs
3
Q
Max Landing Weight
A
3800 lbs
4
Q
Max Weight in Baggage Compartment
A
200 lbs
5
Q
Fuel Capacity
A
110 gal (55 per tank)
6
Q
Usable Fuel
A
108 gal (54 per tank)
7
Q
Positive Load Factor
A
Flaps Up 3.8 Gs
Flaps Down 2 Gs
8
Q
Negative Load Factor
A
Not approved for inverted flight
9
Q
Accelerate-stop distance
A
Distance required to accelerate to Vr, experience an engine failure, and bring the aircraft to a stop
10
Q
Takeoff ground roll- Short field effort
A
The takeoff ground roll in a short-field takeoff refers to the distance an aircraft travels along the
runway from the moment it starts its takeoff roll until it becomes airborne.
11
Q
Accelerate-go distance
A
Distance required to accelerate to Vr, experience an engine failure, continue the takeoff, and climb to
50’ AGL
12
Q
V1
A
Critical engine failure speed or takeoff decision speed
13
Q
V2
A
Takeoff safety speed, or a referenced airspeed obtained after lift-off at which the required
one-engine-inoperative climb performance can be achieved
14
Q
Service ceiling
A
The highest altitude at which the airplane can maintain a 100 fpm climb rate (both engines
operating)
15
Q
Absolute ceiling
A
The altitude where climb is no longer possible (0 fpm)
16
Q
Single engine service ceiling
A
The highest altitude at which the plane can maintain a 50 fpm climb rate with one operating engine
(operating at full power, inoperative feathered)
17
Q
What happens if you are above the single engine absolute ceiling and lose an engine? How do you
minimize descent?
A
The airplane will drift down to its single engine absolute ceiling. Vyse (blueline) yields a minimum
sink above the single engine absolute ceiling.
18
Q
Critical Density Altitude
A
The density altitude at which Vs and Vmc are the same. Vs remains the same as altitude is increased
whereas Vmc decreases with altitude, as will be explained further later in this document.
19
Q
Maximum Zero Fuel Weight
A
The maximum allowable weight of an aircraft, excluding the weight of any usable fuel. It includes the
weight of the aircraft structure, payload (passengers, cargo, baggage), crew, and any other operational
items on board, but it specifically excludes the weight of the fuel itself. Exceeding the MZFW could
compromise the structural integrity, performance, and safety of the aircraft.
20
Q
Conventional twin
A
Both propellers rotating in the same direction (usually clockwise from the pilot’s perspective)
21
Q
Critical engine
A
The engine, if it were to fail, would most adversely affect the performance/handling of the airplane.
In a conventional twin this is the left engine.
22
Q
Do we have a critical engine in the seminole?
A
No, because we have counter-rotating props.
23
Q
PAST
P-Factor (Yaw)
A
Comm multi answer: At higher angles of attack, the descending blade takes a bigger bite out of the
air, producing more thrust. In a conventional twin, the descending blade on the right engine has a
longer arm to the CG of the airplane than the descending blade on the left engine. This longer arm
creates a greater yawing moment if the left engine is inoperative, meaning that it is the critical engine.
MEI answer: At higher angles of attack, the descending blade has a higher angle of attack than the
ascending blade, taking a bigger bite out of the air, thus producing more thrust. In a conventional
twin, the descending blade (the right side on both engines) on the right engine has a longer arm
from the CG than the descending blade on the left engine. Using the formula THRUST x ARM =
MOMENT, you can see that this longer arm creates a bigger asymmetric thrust moment from the
operating engine, resulting in a larger yawing moment. The greater resulting yawing moment from
the left engine being inoperative makes it the critical engine.
In a counter-rotating twin, the arms of the descending blades are the same, meaning there is no
critical engine.
24
Q
PAST
Accelerated Slipstream (Roll)
A
Comm multi answer: This can be related to P-Factor in that the descending blade produces more
thrust, meaning it is accelerating more airflow behind it than the ascending blade. Since the right
engine descending blade is further away from the CG, the accelerated airflow is creating greater lift
more outboard on the wing. This longer arm creates a greater rolling moment if the left engine is
inoperative, meaning that it is the critical engine.
MEI answer: The propellers accelerate air behind them and the more thrust they are creating, the
more air they are accelerating. This relates to P-Factor in that the descending blade produces more
thrust and thus the right side of each engine is having more accelerated slipstream. This greater
airflow creates more lift on that surface of the wing. The surface of the wing that is creating more
lift is further from the CG (greater arm) for the right engine, creating a greater moment, and thus
resulting in a larger rolling moment. The greater resulting roll moment from the left engine being
inoperative makes it the critical engine.
In a counter-rotating twin, the arms of the descending blades are the same, meaning there is no
critical engine.
25
PAST
Spiraling Slipstream (Yaw)
Comm multi answer: This can also be related back to P-Factor in that the descending blade
producing more thrust creates a relative lower pressure than the ascending blade. This causes the
spiraling slipstream behind the propellers to drift towards that relative lower pressure, which is to the
right for both engines in a conventional twin. The right engine spiraling slipstream drifts off into the
ambient air while the left engine spiraling slipstream drifts and strikes the vertical stabilizer. Since
that increases airflow over the vertical stabilizer, it makes the rudder more effective. It also slightly
pushes against the left side of the vertical stabilizer. With the loss of airflow due to the left engine
being inoperative, and the lack of airflow hitting the left side of the vertical stabilizer to “correct”
asymmetric thrust, makes it the critical engine.
MEI answer: Due to the spinning of the propeller, it causes the airflow behind it to corkscrew. And
relating back to P-Factor, at higher angles of attack, the greater thrust being created by the
descending blade on the right side of the engine leads to an area of relative lower pressure. As high
pressure always seeks low pressure, the corkscrew slipstream drifts to the right. This slipstream from
the right engine drifts right into the ambient air whereas the slipstream from the left engine strikes
the vertical stabilizer. This increases the airflow over the vertical stabilizer, rendering it more
effective as less rudder deflection is needed to counteract the asymmetric thrust created by the
operating engine. The slipstream also strikes the tail from a slight angle on the left side, assisting to
yaw the nose to the left, which would help to counteract some of asymmetric thrust to the right
from the left engine being the only one operating. The loss of airflow over the vertical stabilizer due
to the left engine being inoperative leads to a combination of the loss of rudder effectiveness and
the lack of a “correcting” yawing force, making it the critical engine.
In a counter-rotating twin, spiraling slipstreams from the propellers both drift towards the vertical
stabilizer, meaning there is no critical engine.
26
What is Vmc? (*HAVE THIS DEFINITION MEMORIZED*)
The calibrated airspeed at which, when the critical engine is suddenly made inoperative, it is possible
to maintain control of the airplane with that engine still inoperative and maintain straight flight with
an angle of bank of not more than 5 degrees.
Definition per 23.149 (historical reg) when the Seminole was certificated.
27
PAST
Torque Effect (Roll)
Comm multi answer: Newton’s Third Law states that for every action, there is an equal and opposite
reaction. As the engine spins clockwise, it imparts a counter-clockwise rolling force on the airplane.
In a conventional twin that means both engines try to roll the plane to the left. An inoperative right
causes the plane to roll to the right and an inoperative left engine causes the plane to roll to the left.
Since the left rolling tendency created by the right engine will compound with the left rolling
tendency of the inoperative left engine, the left engine is the critical engine.
MEI answer: Newton’s Third Law states that for every action, there is an equal and opposite
reaction. As the engine spins clockwise, it imparts a counter-clockwise rolling force on the airplane.
An inoperative right engine means that there is a right roll tendency (due to the still operating left
engine). But the left engine is imparting a left roll tendency to the plane (while still operating, due to
torque effect), partially canceling out the rolling tendency of having an inoperative engine. If the left
engine is inoperative then there is a left roll tendency (due to the operating right engine) and the
right engine is imparting a left roll tendency to the plane (while still operating), compounding the
rolling tendency, making the left engine the critical engine.
In a counter-rotating twin, the torque effect of both engines counteract adverse roll, meaning there
is no critical engine.
28
SMACFUM (14 CFR 23.149) Factors that affect Vmc (conditions under which it was determined)
Why do we still care about 23.149 if it’s a historical regulation? What did it lay out?
Because this FAR was current when the Seminole was originally certificated
These factors were set in place to standardize the parameters in which Vmc was determined in order
to prevent manufacturers from advertising really low Vmc speeds by having the plane in unrealistic
attitudes/configurations. They are meant to essentially simulate the worst case scenarios.
29
SMACFUM (14 CFR 23.149)
Standard day, Sea level
Denser air (on a standard day at sea level) yields greater performance than less dense air (at a higher
density altitude) since we are naturally aspirated.
As density altitude increases (either with an increase in altitude or increase in temperature),
performance decreases since the air is less dense. The engine (if naturally aspirated) and the
propellers don’t work as efficiently in lower density air. The operating engine creates more
asymmetric thrust in denser air than in thinner air, meaning that more rudder is needed to
counteract it. This leaves less rudder available to counteract asymmetric thrust the slower you go (as
airflow decreases, greater deflection is needed to achieve the same result), decreasing controllability.
The lower the density altitude (more dense air), the worse it is for Vmc. So a standard day at sea level
(compared to a higher density altitude) will increase Vmc.
30
SMACFUM (14 CFR 23.149)
Max power on operating engine
Operating an engine at max power will yield greater performance than operating at partial power.
As power is increased on the operating engine, greater asymmetric thrust is created. The greater the
asymmetric thrust, the more rudder is needed in order to counteract the resulting yaw, which leaves
less rudder available, decreasing controllability. So as power is increased on the operating engine,
Vmc will increase.
31
SMACFUM (14 CFR 23.149)
Aft CG
An aft CG requires less tail downforce, decreasing drag and total lift needed. It is also harder to stall,
gives a higher cruise speed, and increases endurance/range.
As CG is moved further aft, the arm between the CG and the rudder decreases, lowering the
effectiveness of the rudder. This means that you are going to need greater rudder travel or a faster
speed in order to achieve the same results, which leaves you less rudder available, decreasing
controllability. You can relate this back to the formula above and see that a shorter arm to the
rudder means more rudder force is needed. So as CG is moved further aft, Vmc will increase.
32
SMACFUM (14 CFR 23.149)
Critical prop windmilling
A windmilling propeller creates a significant amount of (parasite) drag, much more than a feathered
propeller. The extra drag adds to yaw due to the asymmetric thrust created by the operating engine,
further yawing the airplane towards the inoperative engine. This requires even more rudder to
counteract that yaw. This leaves less rudder available, decreasing controllability. So with the critical
propeller windmilling, Vmc will increase.
With all this drag, performance will decrease.
How to
33
SMACFUM (14 CFR 23.149)
Flaps takeoff (up in the Seminole), Gear up
When the flaps are down, the wings create more lift overall, but with lift also comes (induced) drag.
The side with the operating engine is creating more lift due to the accelerated slipstream. That
accelerated slipstream creates more lift on that wing, but also more induced drag. The flap is also in
the airflow behind the engine and creates parasite drag. This drag on the side of the operating engine
is counteracting the yaw from the asymmetric thrust, resulting in less rudder required to maintain
heading. Having the flaps out also creates a stabilizing effect on the airplane. Without the flaps down
to help stabilize, there is less rudder available, decreasing controllability. So with the flaps up, Vmc
will increase.
*When talking about the drag created by the flaps, simplify it by just saying that with the flaps down,
more drag is produced. Above is more of an in depth explanation as to why that is the case.*
When the gear is down, the keel effect allows for the stabilizing of the aircraft with the relative wind.
The accelerated slipstream of the gear behind the engine also creates further drag on the side of the
operating engine, helping to counteract the yaw from the asymmetric thrust. Without the gear down
to help stabilize, there is less rudder available, decreasing controllability. So with the gear up, Vmc
will increase.
But, since flaps and gear create drag, when they are retracted performance increases.
34
SMACFUM (14 CFR 23.149)
Up to 5° of bank into operating engine
When the aircraft is banked, the lift created is divided into both a vertical and horizontal component.
The bank into the operating engine creates a horizontal component of lift that helps counteract the
yaw from the operating engine. This then means that less rudder is needed to counteract that yaw.
Also, when the wings are level (and the ball centered), asymmetric thrust leads to the airplane being
in a side-slip condition. The relative wind is hitting the airplane from an angle and this creates excess
drag. When you have up to 5° of bank into the operating engine (and the ball split), a zero sideslip
condition exists as the relative wind is in line with the longitudinal axis of the airplane, resulting in
the minimum drag possible with a failed engine. So with 5° of bank into the operating engine, Vmc
will decrease.
Greater bank angles will decrease Vmc more as less rudder will be needed to counteract yaw from
the asymmetric thrust but they are not realistic and will also lead to a greater loss in the vertical
component of lift to keep the aircraft flying. And greater bank angles will lead the aircraft to be in a
slipping condition, increasing overall drag.
35
SMACFUM (14 CFR 23.149)
Most unfavorable weight
The most unfavorable weight in a multi engine piston (in relation to Vmc) is light. That is because
the heavier the airplane, the greater the lift that is required to maintain level flight (to equal the
weight). As the aircraft banks (as in the above) the lift is separated into vertical and horizontal
components. The greater the overall lift being produced (due to the higher weight), the greater
amount of horizontal lift will then be produced when the airplane banks. The greater amount of
horizontal component of lift helps counteract the yaw from the asymmetric thrust and means that
less rudder is needed. So as weight decreases, Vmc increases.
36
Why is there a greater loss of performance than thrust when an engine is lost?
This has to do with excess thrust. The Seminole produces 360 hp total (180 hp per engine) and say,
for example, it takes 160 hp to maintain level flight. With both engines operating, there is 200 hp of
excess thrust that allows for climb or an increase in airspeed. When one engine fails, 180 hp is lost
(half of the power). But suddenly there is only 20 hp of excess thrust available to climb or increase
airspeed (90% of the performance). So with a 50% decrease in power (360 hp→180 hp), there is a
90% decrease in performance/excess thrust (200 hp→20 hp).
37
Aerodynamics of a single engine
When an engine fails, the yaw created by the operating engine is needed to be counteracted by
rudder input. This rudder input (with wings level) may center the ball but it puts the airplane into a
sideslip condition as the relative wind is coming the side of the inoperative engine (since the flight
path of the aircraft isn’t straight ahead in the longitudinal axis of the plane, it’s slightly sideways).
This sideslip creates excess drag, which we want to avoid, especially with the 90% decrease of
performance we have when losing an engine. In order to get rid of this excess drag we want to get
the plane into a zero sideslip condition. This is done by banking 2-3° into the operating engine and
splitting the ball (½ ball deflection into the operating engine). This will make the plane push through
the air with the asymmetric thrust and the relative wind will be coming from more head on with the
longitudinal axis of the plane and be in a zero sideslip condition.
38
SMACFUM Table
39
Forward CG
- Increased longitudinal stability
- Lower cruise speed
- Higher stall speed
- Easier stall recovery
40
Aft CG
- Decreased longitudinal stability
- Higher cruise speed
- Lower stall speed
- Harder stall recovery
41
Weight and Balance Review
- Arm: The horizontal distance from the reference datum
- CG: The point at which an airplane would balance if suspended. It is also the place at which
the airplane rotates around its different axes.
- Moment: The force that tries to cause rotation. The product of the weight multiplied by
arm
42
Engine
Lycoming O-360-A1H6 (left engine) + LO-360-A1H6 (right engine), Both 180 hp @ 2700 rpm
L on the right engine stands for “Left” due to the left rotation of the propeller (counter rotating)
They are carbureted, Horizontally opposed, Air cooled, Naturally aspirated, Direct drive
43
Induction
Air for combustion comes over to the air filter on the left side of the engine (when
looking from the front) and through the induction air box mounted on the bottom rear of the
engine and to the carburetor. This induction box has a manually operated two-way valve that allows
the carburetor to receive either induction air through the air filter or carb heat air that is unfiltered
and heated by the exhaust through a shroud. This heated air is less dense and will lead to a decrease
in performance.
Since the carb heat air is not filtered, it should not be selected during ground ops due to the risk of
dust or contaminants entering the engine.
44
Cowl Flaps
Manually operated flaps (via handles on the bottom of the pedestal) that change the
amount of air flowing through the engine cowling and helps facilitate cooling.
ATP max speed: 100kts & keep closed if ambient temperature is 40°F or less
45
Oil System
Wet sump system, 2 quarts minimum (6.5 per ATP), 8 quarts maximum)
46
Propellers
Two bladed, 74”, controllable pitch, constant speed, full feathering, aluminum prop (can be shaved
down to 72”)
Counter rotating system, not conventional
Props can be shaved down to 72 inches minimum (1 inch per side), this can be found in the
Limitations (Section 2) of POH
47
Prop System
The pitch of the blade is controlled through oil pressure. Inside the prop hub there is a spring and
nitrogen stored under pressure as well as counterweights on the base of the blades that work to
constantly bring the blades into a high pitch or feathered position. Opposing this force is oil
pressure that pushes against a piston.
48
What wants to constantly feather the prop?
1) Nitrogen
2) Hub spring
3) Counterweights
49
What keeps the prop from feathering?
Oil pressure
50
Which ones bring it to high vs low pitch?
The Nitrogen, Hub spring, and Counterweights bring it to high pitch/feather, while oil pressure
brings to low pitch
51
What does low vs high pitch mean?
Low pitch means a low angle of attack, allowing the prop to spin faster. This looks like a flat blade
angle when viewing it from the front of the plane. The opposite is the case for high pitch.
52
Why is it desirable to bring the prop to feather in a failure scenario if that is technically high pitch?
When the prop is spinning, it is spinning so fast (faster than the plane is moving forward) that the
relative wind is coming from the direction in which the prop is spinning, so a low pitch (or AOA) is
one that allows the prop to cut through the relative wind as cleanly as possible. A high pitch curves
the props (more backwards) to have a higher AOA to this relative wind. But when the engine is shut
down, it wants to go to full feather (technically high pitch) because then it is actually angled into the
relative wind and gives it the smallest profile as the relative wind is now coming from the front due
to the forward movement of the plane through the air.
53
Prop governor
The prop governor helps regulate the pitch of the propellers by varying the oil pressure in the prop
system in order to maintain a constant rpm (as selected by the pilot via the prop lever).
54
Why does MP increase when you lower the rpms?
As rpm decreases, the pistons are moving slower as well, meaning they are not creating as much
suction. Since MP is reading absolute pressure, less suction means an increase in pressure in the
carburetor and thus a rise in the MP indication.
55
Why is power regulated with rpms and not MP on the ground?
Because the prop governor is on the mechanical low pitch stops and does not have enough
windmilling from oncoming airflow to be able to maintain rpm.
56
If we experienced carb icing in the air and need to use carb heat, what indication would be receive
on our instruments?
A drop in Manifold Pressure
57
What would you do if the unfeathering accumulator didn’t work?
Use the starter to bump start the engine.
58
Flaps
Manually operated (via a Johnson bar) plain flaps with 0°, 10°, 25°, & 40° detents. At 25° & 40°,
they become slotted flaps. They are spring loaded to return to 0°.
59
Stabilator
The entire horizontal tail surface moves. It is mounted with an anti-servo tab that also acts as a trim
tab operated by a control wheel between the two front seats. An anti-servo trim tab moves in the
same direction as the control surface (stabilator), essentially increasing the camber and thus the
chord line of the aerodynamic surface. This then increases the angle of attack of the surface,
increasing the control feel and decreases the likelihood of overcontrolling the airplane.
60
Rudder
The rudder is also mounted with an anti-servo trim tab that acts as a trim tab and is operated by a
control wheel between the two front seats.
The top of the vertical stabilizer (just under the stabilator) has a set of 6 pins (3 per side) that are
called Hi-Lok pins. These lock the stabilator in to the rest of the tail.
61
Brake System
The brakes are single disc, double puck and are on each main gear. They are operated hydraulically
via toe brakes on the rudder pedals. The brake hydraulic system reservoir is located in the upper
right side of the bulkhead in the nose and is independent of the one used to operate the landing
gear.
62
What would give you a gear unsafe indication?
When all three down limit or all three up limit switches are not actuated.
63
What is the purpose of the gear horn?
The gear horn is there to prevent you from landing with the gear up by notifying you when you are
in a configuration for landing
64
What would sound off the gear horn?
1. MP below 15” with gear up (varies as it’s actuated by microswitches in the throttle quadrant)
2. Flaps 25 or 40 with gear up
3. Putting the gear selector in the up position while on the ground
65
What happens when the pressure in the system drops?
The pump will activate to bring the pressure back up to 1875 psi and then shut off.
66
What happens if the high pressure switch malfunctions and the pump doesn’t shut off?
The pump would keep pumping but the High Pressure Control would open and relieve the pressure
in the system. You would be able to notice that the pump is still operating by verifying the ammeter
load.
67
What happens if the pump doesn’t shut off once the gear is down and locked?
The pump would keep pumping but the Low Pressure Control would open and relieve the pressure
in the system. You would be able to notice that the pump is still operating by verifying the ammeter
load.
68
Stall Tabs
There are two stall tabs on the leading edge of the left wing to provide adequate stall warning in
various configurations. The outboard stall tab is activated when the flaps are at 0° and 10°, while the
inboard stall tab is activated when the flaps are at 25° and 40°. They operate by the airflow forcing
them down and then once reaching the critical AOA, they will fall back and activate the switch and
sound the stall horn. The right squat switch disables the stall tabs on the ground.
69
You are cruising and have burned more fuel from the left tank, how you configure the fuel selectors
in order to level the tanks?
You will have the Left Fuel Selector in the XFEED position and the Right Fuel Selector in the ON
position. You want the right engine to pull from the right tank (it’s own tank) and the left engine to
also pull from the right tank (the opposite tank).
70
You have a right engine failure. How would you configure the fuel selectors if you plan extended
ops? Which Aux Fuel Pump will you have on?
You will have the Left Fuel Selector in the ON or XFEED position and the Right Fuel Selector in
the OFF position. The Left Aux Fuel Pump will be on since it is after the Fuel Selector.
71
What if the boost pump is inside the fuel tank and you need to crossfeed in the above example?
In this case, you would have the Right Aux Fuel Pump on whenever you are drawing from the right
tank.
72
What endorsements does a Comm Single to a Comm Multi add on need?
61.39(a)(6)(i) and (ii) - Prerequisites for the practical test and training in the last 2 calendar months
61.63(c) per 61.127(b)(2)(i-xi) - Class change and flight proficiency
61.31(e) - Complex endorsement
73
What endorsements does an MEI add on need?
61.39(a)(6)(i) and (ii) - Prerequisites for the practical test and training in the last 2 calendar months
61.191 per 61.187(b)(2)(i-xv) - MEI flight proficiency
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