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28 February 2008 D S Puttock based on the work ofWG Scull

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The Manoeuvring Envelope

The placard, structure and flight

limitations

Part 2

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L o a

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-1

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Kt

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StallLine

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FLIGHT NOT

POSSIBLEFLIGHT

POSSIBLE

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StallLine

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StallLine

LoadFactor

Stallspeed(Kt)

0 0

0.1 12

0.25 19

0.5 27

1.0 38

1.035 39

1.15 41

1.41 45

2 54 3.8 74

5.76 91

11.5 129

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StallLine

LoadFactor

Stallspeed(Kt)

0 0

0.1 12

0.25 19

0.5 27

1.0 38

1.035 39

1.15 41

1.41 45

2 54 3.8 74

5.76 91

11.5 129

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StallLine

LoadFactor

Stallspeed(Kt)

0 0

0.1 12

0.25 19

0.5 27

1.0 38

1.035 39

1.15 41

1.41 45

2 54 3.8 74

5.76 91

11.5 129

Vs=1gstall speed

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StallLine

LoadFactor

Stallspeed(Kt)

0 0

0.1 12

0.25 19

0.5 27

1.0 38

1.035 39

1.15 41

1.41 45

2 54 3.8 74

5.76 91

11.5 129

Typicalcamberedaerofoil, workspoorly upsidedown

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L o a

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20 40 60 80 100 120 140 160Normalgravity

VD

Design dive speed

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VD

Design dive speed

Several calculations to derive V D.

Gliders built under JAR-22 areeither utility or aerobatic category.

VNE and not V D appears on theplacard

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VDVelocity never exceed

.

VNE

VNE is usually 90% of V D

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VDDemonstrated design speed

.

VNE

VDF is approximately95% of V DDuring test flying, theglider is flown to theDemonstrated designSpeed

VDF

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VD

.

VNEVDF

LIMIT LOADS

JAR-22 sets+4g As the limit load forCategory U

gliders at V D, and5.3g at the stall line

n 2

n 1

n 3

n 4

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L o a

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.

n 2

n 1

n 3

n 4

UCategory

Acategory

n1 +5.3 +7.0 n2 +4.0 +7.0 n3 -1.5 -5.0 n4 -2.65 -5.0

Envelope corners

Limit load

Limit load

7

-5

A Category

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.

7

8

The factor of safety required by JAR-22 isthe limit loadmultiplied by1.5.

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.

VA

5.3

The maximummanoeuvring speedV A, is where the 5.3glimit line crosses thestall line

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.

SUMMARY

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The Gust Envelope

The placard, structure and flightlimitations

Part 3

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L o a

d F

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.

A very sudden gustWill not instantlyStall the wing

Creation of the gust envelope

Briefly the wing canProduce 25% moreLift.

Load factors canIncrease by 25%As a result

VNEVD

Stall line revised

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.

Creation of the gust envelope

VNEVD

JAR-22.333 At VB sailplane

must be capableOf withstandingpositive up andnegative downgusts of 15 m/s

This is defined As a strong gust And is about 30kts

VB

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.

Creation of the gust envelope

VNEVD

Rough air is allair in lee-wave

rotors,thundercloudsvisible whirlwindsor over mountaincrests

VB

VA cannot be moreThan VB

In practice they areoften very close.

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.

Creation of the gust envelope

VNEVD

VBStrong gusts arenot an issue upto VB(Max Rough Air)

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L o a

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Kt

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.

Creation of the gust envelope

VNEVD

VBEXAMPLE

Sailplane at 110ktsmeets a weak gust.

Effect of gust

Effect ofNormal flight

If the glider pulls3g in a loop, atthe same moment.The aircraft will beOutside the placardedLimits.

AdditionalEffect of loop