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The Manoeuvring Envelope

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The Manoeuvring Envelope

Part 2

The placard, structure and flight limitations

D S Puttock based on the work of WG Scull

6

5

4

3

2

Load Factor,n

1

Kt

0

20

40

60

80

100

120

140

160

-1

-2

-3

D S Puttock based on the work of WG Scull

-4

6

5

4

3

2

Load Factor,n

1

Kt

0

20

40

60

80

100

120

140

160

-1

-2

-3

D S Puttock based on the work of WG Scull

-4

6

Stall

Line

5

4

3

2

Load Factor,n

1

Kt

0

20

40

60

80

100

120

140

160

-1

-2

-3

D S Puttock based on the work of WG Scull

-4

6

5

FLIGHT NOT

POSSIBLE

4

FLIGHT

POSSIBLE

3

2

Load Factor,n

1

Kt

0

20

40

60

80

100

120

140

160

-1

-2

-3

D S Puttock based on the work of WG Scull

-4

6

Stall

Line

5

4

3

2

Load Factor,n

1

Kt

0

20

40

60

80

100

120

140

160

-1

-2

-3

D S Puttock based on the work of WG Scull

-4

6

Stall

Line

5

4

3

2

Load Factor,n

1

Kt

0

20

40

60

80

100

120

140

160

-1

-2

-3

D S Puttock based on the work of WG Scull

-4

6

Stall

Line

5

4

3

2

Load Factor,n

1

Kt

0

20

40

60

80

100

120

140

160

-1

-2

-3

D S Puttock based on the work of WG Scull

-4

6

Stall

Line

5

Vs=1g stall speed

4

3

2

Load Factor,n

1

Kt

0

20

40

60

80

100

120

140

160

-1

-2

-3

D S Puttock based on the work of WG Scull

-4

6

Stall

Line

5

4

3

2

Load Factor,n

1

Kt

0

20

40

60

80

100

120

140

160

Typical cambered aerofoil, works poorly upside down

-1

-2

-3

D S Puttock based on the work of WG Scull

-4

6

5

4

3

2

Load Factor,n

1

Kt

0

20

40

60

80

100

120

140

160

-1

-2

-3

D S Puttock based on the work of WG Scull

-4

Design dive speed

VD

6

5

4

3

2

Load Factor,n

1

Kt

0

20

40

60

80

100

120

140

160

Normal

gravity

-1

-2

-3

D S Puttock based on the work of WG Scull

-4

Design dive speed

VD

6

Several calculations to derive VD.

Gliders built under JAR-22 are either utility or aerobatic category.

VNE and not VD appears on the placard

5

4

3

2

Load Factor,n

1

Kt

0

20

40

60

80

100

120

140

160

-1

-2

-3

D S Puttock based on the work of WG Scull

-4

Velocity never exceed

VNE

VD

6

.

5

VNE is usually 90% of VD

4

3

2

Load Factor,n

1

Kt

0

20

40

60

80

100

120

140

160

-1

-2

-3

D S Puttock based on the work of WG Scull

-4

Demonstrated design speed

VNE

VD

VDF

6

.

5

VDF is approximately

95% of VD

During test flying, the glider is flown to the

Demonstrated design

Speed

4

3

2

Load Factor,n

1

Kt

0

20

40

60

80

100

120

140

160

-1

-2

-3

D S Puttock based on the work of WG Scull

-4

VNE

VD

VDF

6

.

n1

5

n2

4

3

LIMIT LOADS

JAR-22 sets+4g

As the limit load for

Category “U”

gliders at VD, and

5.3g at the stall line

2

Load Factor,n

1

Kt

0

20

40

60

80

100

120

140

160

-1

n3

-2

n4

-3

D S Puttock based on the work of WG Scull

-4

VNE

VD

VDF

Limit load

6

.

n1

5

n2

4

3

2

Load Factor,n

1

Kt

0

Envelope corners

20

40

60

80

100

120

140

160

-1

n3

-2

n4

-3

Limit load

D S Puttock based on the work of WG Scull

-4

7

A Category

6

Limit load

.

n1

5

n2

4

3

2

Load Factor,n

1

Kt

0

20

40

60

80

100

120

140

160

Envelope corners

-1

n3

-2

n4

-3

Limit load

-4

D S Puttock based on the work of WG Scull

-5

Failure!

8

Ultimate load

7

6

Damage

.

5

Limit load

Load Factor,n

4

3

2

The factor of safety required by JAR-22 is the limit load multiplied by1.5.

1

Kt

0

20

40

60

80

100

120

140

160

D S Puttock based on the work of WG Scull

6

.

5.3

5

4

3

VA

2

Load Factor,n

1

Kt

0

20

40

60

80

100

120

140

160

The maximum manoeuvring speed VA, is where the 5.3g limit line crosses the stall line

-1

-2

-3

D S Puttock based on the work of WG Scull

-4

SUMMARY

Failure

6

Flight not

possible

.

Damage

5

4

3

Failure

2

Load Factor,n

OK

1

Kt

0

20

40

60

80

100

120

140

160

-1

OK

Flight not

possible

-2

Damage

-3

Failure

D S Puttock based on the work of WG Scull

-4

The Gust Envelope

Part 3

The placard, structure and flight limitations

D S Puttock based on the work of WG Scull

Creation of the gust envelope

A very sudden gust

Will not instantly

Stall the wing

6

Stall line revised

.

Briefly the wing can

Produce 25% more

Lift.

5

VNE

VD

4

3

2

Load Factor,n

1

Kt

0

20

40

60

80

100

120

140

160

Load factors can

Increase by 25%

As a result

-1

-2

-3

D S Puttock based on the work of WG Scull

-4

Creation of the gust envelope

JAR-22.333

At VB sailplane

must be capable

Of withstanding

positive up and

negative down

gusts of 15 m/s

6

VB

.

5

VNE

VD

4

3

2

Load Factor,n

1

Kt

This is defined

As a strong gust

And is about 30kts

0

20

40

60

80

100

120

140

160

-1

-2

-3

D S Puttock based on the work of WG Scull

-4

Creation of the gust envelope

Rough air is all

air in lee-wave

rotors,

thunderclouds

visible whirlwinds

or over mountain

crests

6

VB

.

5

VNE

Strong gust

+15 m/s

VD

4

3

2

Load Factor,n

1

Kt

VA cannot be more

Than VB

In practice they are

often very close.

0

20

40

60

80

100

120

140

160

-1

Strong gust

+15 m/s

-2

-3

D S Puttock based on the work of WG Scull

-4

Creation of the gust envelope

6

VB

.

Strong gusts are

not an issue up

to VB

(Max Rough Air)

5

VNE

Strong gust

+15 m/s

VD

4

3

2

Load Factor,n

1

Kt

0

20

40

60

80

100

120

140

160

-1

Strong gust

+15 m/s

-2

-3

D S Puttock based on the work of WG Scull

-4

Creation of the gust envelope

6

VB

.

Weak gust

+7.5 m/s

Strong gusts are

not an issue up

to VB

(Max Rough Air)

5

VNE

VD

4

3

2

Load Factor,n

1

Kt

0

20

40

60

80

100

120

140

160

Weak gusts are

+7.5 m/s

-1

Weak gust

+7.5 m/s

-2

-3

D S Puttock based on the work of WG Scull

-4

Creation of the gust envelope

Additional

Effect of loop

EXAMPLE

6

VB

.

Weak gust

+7.5 m/s

Sailplane at 110kts

meets a weak gust.

5

VNE

VD

4

Effect of gust

3

2

Load Factor,n

Effect of

Normal flight

1

Kt

If the glider pulls

3g in a loop, at

the same moment.

The aircraft will be

Outside the placarded

Limits.

0

20

40

60

80

100

120

140

160

-1

Weak gust

+7.5 m/s

-2

-3

D S Puttock based on the work of WG Scull

-4