V-SPEEDS

Question 1

Go through the V-speeds from start to finish and place them in the correct order?

Answer 1

Vmcg Vef V1 Vmbe Vmca Vr Vs Vmu Vlo V2

Question 2

Define “Vmcg”

Answer 2

Lowest speed that provides directional control on the ground with the critical engine inoperative

Question 3

What factors affect Vmcg

Answer 3

Density. Thrust varies with density therefore the assymetric moment is higher when density is higher. That is at low altitudes and low temperatures

Question 4

Describe the certification rules for Vmcg

Answer 4

Steering can’t be used Max 30 ft lateral excursion from the centerline is permitted

Question 5

What is Vmcg:s relationship with V1?

Answer 5

Vmcg has to be equal or lower than V1

Question 6

When might V1 be lower than Vmcg?

Answer 6

At low weights and altitudes At low weights V1 can be reduced At low altitudes Vmcg might be higher than V1 due the increased turning moment

Question 7

Define Vef?

Answer 7

The speed at which an engine failiure occurs, to be recognised at V1.

1 second reaction time is used

Upon recognition at V1, 2 seconds are given to react to close the throttles

Question 8

Definition of V1?

Answer 8

Min speed to accept an engine failure and continue T/O and make V2 by 35 ft within TODA

and

Max speed to reject T/O and stop with in ASDA

Question 9

How do you get your Field limited take-off mass?

Answer 9

Merge the Vstop and Vgo graphs

Vstop: V on vertical axis, T/O mass on horizontal axis.

As mass increases the speed at which we need to stop decreases

Vgo: As T/O mass increases the speed at which we to go increases.

Question 10

Limitaions on V1?

Answer 10

1. Can’t be greater than Vr but equal
2. Can’t exceed Vmbe
3. V1 must be faster than Vmcg

Question 11

Why is a high V1 speed choosen, if possible?

Answer 11

As to delay the “must-go” descision as it is safer to be on the ground.

If an a/c is T/O mass is climb- or obstacle limited an as high as possible V1 is choosen to get good climb performance

Question 12

What does an increase in V1 means in terms of ASD and TOD?

Answer 12

ASD increases, higher abort speed that eats more runway

TOD decreases

Question 13

What happens to V1 when density is reduced?

Answer 13

We’ll have less thrust which, on a limiting T/O, the reduced acceleration means we won’t make V2 by 35 ft within TODA.

We must then increase V1. On a balanced field the increased V1 would lead to a decrease in mass

Question 14

What are the correction made for V1 with regards to:

1. Slope
2. Wind
3. Altitude
4. Temperature
5. Weight

Answer 14

1. Slope: Upslope increases V1, down slope decreases V1
2. Wind: Headwind increases V1, tailwind decreases V1
3. Altitude: Altitude increases V1
4. Temperature: Temp increase increases V1
5. Weight: More weight increases V1

Reduced stopping capability calls for lower V1

Reduced acceleration capability calls for a higher V1

Question 15

How does slippery runways, with no roll resistance affect V1?

Answer 15

Reduced stopping action reduces V1

Since there’s no reduced acceleration there’s no correction for that.

What happens is that V1 reduces

Question 16

How does a slippery runway, with roll resistance, affect V1?

Runway has snow, slush or more than 3 mm standing water

Answer 16

Reduced stopping action lowers V1

Reduced acceleration action increases V1

What’s happening is that V1 doesn’t change

Question 17

Definition of Vmbe?

Answer 17

It’s the lowest CAS at which the brakes can absorb all the energy from a rejected T/O at V1

For a mass travelling at a True GS, the kinetic energy is 1/2 MV²

When braking, this energy goes into the brakes as heat

V = a True GS, so the corresponding IAS varies with

• Alt, temp, wind and slope

Question 18

What is V_mbe:s relationship to V1?

Answer 18

V_mbe has to be equal or greater than V1

Question 19

When is V_mbe slowest and most likely to be limited by V1?

Answer 19

V_mbe is slowest and most likely to be limited by V1, when the aircraft is:

1. Heavy
2. High pressure alt, for same IAS/CAS the true GS will be higher which leads to more brake energy needed
3. High temp, same reason as above
4. Tailwind, slow CAS due to less air into pitot tube means that for the same CAS the true GS will be higher

Question 20

What are the corrections made for V_mbe with regards to:

1. Slope
2. Wind
3. Altitude
4. Weight
5. Temperature

Answer 20

1. Slope: V_mbe decreases with downslope due to more potential energy, which is harder to stop
2. Wind: Tailwind decreses V_mbe. True GS will be higher for the same CAS in no wind cause less air goes into the pitot tube
3. Altitude: Higher alt will decrease V_mbe cause CAS will be the same but the true GS will be higher
4. Weight: Decresing weight will increase V_mbe
5. Temperature: Lower temp will increase V_mbe

Question 21

What’s the definition of V_mca?

Answer 21

V_mca is the lowest CAS at which the critical engine is suddenly made inoperative where, it’s possible to maintain directional control and stright forward flight with an angle of bank not exceeding 5 degrees

Question 22

How does V_mca change with density?

Answer 22

V_mca is fastest at cold and low airports because the yawing moment is greatest when the air is more dense

Question 23

What is the configuration criteria when deciding V_mca?

Answer 23

MTOW

Most rearward CG

Max 5 deg bank

Full rudder

Critical engine failed

Max contious power on live engine

Question 24

What is the speed limitaion on V_mca?

Answer 24

V_mca may not exceed 1,2 V_s

Question 25

Does V_mca increase or decrease with: 1. Weight increase 2. Fwd CG 3. Altitude increase 4. Incresed bank angle 5. Increasing flap setting

Answer 25

1. Weight increase: V_mca decreases. W adds stability 2. Fwd CG: V_mca decrease 3. Alt increase: V_mca decreases due to lower density 4. Bank angle: V_mca decreases with more bank 5. Flaps: V_mca increases because flaps increase lift and therefore drag

Question 26

What does Vr ensure?

Answer 26

Vr ensures that, in case of engine failure, lift-off is possible and V2 is reached at 35 ft With no engine failure V2 speed is usually higher at 35 ft and is sometimes called V3

Question 27

What is VR:s relationship with V_mu and V_mca?

Answer 27

VR must be such that V_lof is greater than V_mu by 1,10 if all engines are operating or by 1,05 OEI If the a/c is geometrically limited (A318 is not limited) the margins are 1,08 V_mu AEO and 1,04 V_mu OEI VR may not be less than 1,05 V_mca

Question 28

What kind of speed is VR and does it change with density and if so why?

Answer 28

VR is a CAS and shouldn't change with density. However, because VR may not be less than the specified percentages above V_mu and V_mca it is affected by density V_mca increases with higher density (low,cold wx) so to maintain 1,05 V_mca VR must be increased V_mu decreases at low alt, high density airfields At cold, low alt, high density V_mca limits VR At warm, high alt, low density V_mu limits VR

Question 29

Define V_mu?

Answer 29

Is the lowest CAS at which an aeroplane can safely lift off the ground and continue without undue hazard V_mu is related to stall speed out of ground effect

Question 30

Does V_mu vary with density?

Answer 30

Yes it does, unlike a normal stall speed V_mu reduces as air density increases In cold temp and at low alt the density is higher and thrust and it's vertical component is also higher which means that lift required can be achived at a slower CAS

Question 31

Why can an aircraft lift off at V_mu ?

Answer 31

Due to a vertical component of thrust which reduces the actual lift required

Question 32

What may limit V_mu?

Answer 32

Geometry and elevator power capacity

Question 33

Define VLOF ?

Answer 33

The CAS when the aircraft first gets airborne

Question 34

Define V2?

Answer 34

V2 is the minimum speed that should be achieved at 35 ft having suffered a critical engine failure @ V1 It provides the required climb gradient

Question 35

What must V2 not be less than i terms of speeds?

Answer 35

V2 must not be less than: - 1,2 VS and - 1,1 V_mca

Question 36

Why does V2 vary with density? Draw the VS vs V_mca diagram

Answer 36

V2 varies with density It's not V_s that varies but it's V_mca

Question 37

What effect does extending flaps or reducing weight have on V2_min?

Answer 37

Extending flaps or reducing weight decreases V_s Decreasing V_s leads to a decrease in V2_min at airfields with low density (hot, high). This leads to V_mca determining V2_min in more situations

Question 38

When are both V2_min and VR likely to be limited by V_mca?

Answer 38

When: - Temperature is cold - Airport is at low altitude - Flaps are at a high setting - Aircraft is lighter

Question 39

To what speed should V2 ideally be as close to as possible and why?

Answer 39

V2 should be as close as possible to V_md to get max climb gradient in the 2nd segment V2 in itself is usually slower than Vx If the rwy is long enough, increasing VR and V2 speeds could be an option.

Question 40

What the limiting factor for "Tyre speed limitations"?

Answer 40

Limit is a True Ground speed So the limiting IAS and mass will vary with - Altitude - Wind - Flap setting Slope has no effect

Question 41

How does wind affect the Tyre Speed limit?

Answer 41

Tailwind pushes the V_LOF to a slower CAS for the same GS CAS in no wind will be the same for V1/VR in a tailwind but the true GS will be higher with a tailwind due to less air going into the pitot tube which leads to that we have to speed up t get same CAS

Question 42

How does less flaps affect Tyre Speed limit?

Answer 42

Lift off will be at a higher speed with less flaps so therefore the True GS will be higher

Question 43

How does Altitude affect Tyre Speed limits?

Answer 43

CAS for V1 at MSL and 5'000 ft are the same True GS at 5'000 will be higher due to decreased density

Question 44

If Vmcg is limiting, how would you increase aircraft weight?

Answer 44

reduce takeoff thrust, as it is the single engine takeoff asymmetric thrust which dictates Vmcg, along with rudder size.