Limitations and Gust Recovery

Question 1

What’s Vne?

Answer 1

Never exceed speed. It is a structural limitation. Above this speed the high air loads may overstress the airframe to the point of catastrophic faiilure

Question 2

What’ Vno?

Answer 2

maximum IAS for normal oprations. Ensures that, if an event such as a windshear occurs that gives an unexpected increase in IAS, Vne is not exceeded

Question 3

Under what regulations are aircrafts that can operate at higher Mach numbers and altitudes are subject to?

Answer 3

CS 25

Question 4

what’s Mmo?

Answer 4

maximum Mach number. If an aircraft climbs to high altitude at constant IAS, Mach number will increase steadily and eventually we will encounter the problems associate with high speed flight.

Question 5

What’s Vmo?

Answer 5

Is an IAS limit that replaces Vno in the regulations for aircraft under CS 25. This value varies with altitude. Calculated by the air data computer and displayed on the ASI

Question 6

What’s Vle?

Answer 6

(Landing gear extended) maximum safe speed to fly with landing gear extended

Question 7

What’s Vlo?

Answer 7

(Landing gear operating) Max speed to fly with landing gear in transit between one position and the other

Question 8

What’s Vfe?

Answer 8

Max safe speed to gly with flaps extended

Question 9

What’s the relationship between Vs and Load Factor?

Answer 9

Vs varies with the square root of the load factor

Question 10

What happens when load factor reduces below 1 in a pushover?

Answer 10

Vs reduces

Question 11

What are the g limits in CS25?

Answer 11

+2.5 and -1g for transport aircraft flying with flaps up

Extending the flaps increases Clmax and decreases stall speed, while the g limit is reduced by CS25 to 2g, flight envolpe will be reduced in size

Question 12

What’s the ultimate load limit?

Answer 12

IT’s when complete structural failure may occur

Question 13

What are the g limits for other aircrat categories?

Answer 13

L: +3.8g -1.5g
Light Utility: +4.4 g -1.76g
Aerobatic: +6g -3g

Question 14

What’s Va?

Answer 14

Design manoeuvring speed. It’s the speed at which the aircraft will stall when achieving its maximum load factor. For a transport aircraft it will be about 1.58Vs

On aircraft where only one Va is published, maximum mass is assumed

It applies to low level flight only

Question 15

What’s the formula of Va?

Answer 15

Va = > Vs x sqrt(n)

n is the load factor

We must assume that this Va is the publised figure for maxmimum all up mass, and at lighter loads, Va will be less.

Question 16

What’s Vc?

Answer 16

Design Cruise Speed. Set by designer for structural reasons, certification authorities will test the aircraft in level flight up to that speed.
When reaching Vc, an upset mannoeuvre will follow and resulting higher speed will be Vd

Question 17

What’s Vd?

Answer 17

Design dive speed, it is limited by buffet and vibrations

It is Mach limited

Question 18

What happens to the envelope as altitude increases?

Answer 18

They become smaller

Question 19

What’s Vb?

Answer 19

It’s the design speed for maximum gust intensity. This speed is achieved when an aircraft experiences a gust of 66fps while flying at Va

Question 20

How is Vb compared to Va?

Answer 20

It’s a higher EAS and higher load factor than Va

Question 21

What’s Vra?

Answer 21

Rough Air Speed recommended by the aircraft manufacturer for flight in turbulence, and it is a compromise.

Question 22

What’s convection in a turbulent context?

Answer 22

When up draughts and down draughts associated with cumulus cloauds are felt as vertical gusts

Question 23

What factors affect Gust Response?

Answer 23

Speed: if it reduces, alpha must be increased to maintain lift. As speed decreases, gust load factor descreases
Mass: if mass increases, alpha increases, glf decreases
Wing Loading: Wing loading = Weight / Wing area. When a wing requires high values to create the ncessary lift, it has a high wing loading, therefore, when Wing Loading increases, glf decreases
Wing area: if wing area decreases, glf decreases
AR: AR=Span / Chord (determines the shpa e of the lift curve) if AR decreases, glf decreases
Swept wings: increasing the sweep a wing reduces the span, therefore AR decreases and glf decreases
Altitude: as it increases, glf decreases

Question 24

Factors affecting Aerodynamic Ceiling

Answer 24

Mass
1.3 g Buffet Margin
CG
Step Climb