Limitations and Gust Recovery Flashcards
What’s Vne?
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
What’ Vno?
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
Under what regulations are aircrafts that can operate at higher Mach numbers and altitudes are subject to?
CS 25
what’s Mmo?
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.
What’s Vmo?
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
What’s Vle?
(Landing gear extended) maximum safe speed to fly with landing gear extended
What’s Vlo?
(Landing gear operating) Max speed to fly with landing gear in transit between one position and the other
What’s Vfe?
Max safe speed to gly with flaps extended
What’s the relationship between Vs and Load Factor?
Vs varies with the square root of the load factor
What happens when load factor reduces below 1 in a pushover?
Vs reduces
What are the g limits in CS25?
+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
What’s the ultimate load limit?
IT’s when complete structural failure may occur
What are the g limits for other aircrat categories?
L: +3.8g -1.5g
Light Utility: +4.4 g -1.76g
Aerobatic: +6g -3g
What’s Va?
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
What’s the formula of Va?
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.
What’s Vc?
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
What’s Vd?
Design dive speed, it is limited by buffet and vibrations
It is Mach limited
What happens to the envelope as altitude increases?
They become smaller
What’s Vb?
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
How is Vb compared to Va?
It’s a higher EAS and higher load factor than Va
What’s Vra?
Rough Air Speed recommended by the aircraft manufacturer for flight in turbulence, and it is a compromise.
What’s convection in a turbulent context?
When up draughts and down draughts associated with cumulus cloauds are felt as vertical gusts
What factors affect Gust Response?
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
Factors affecting Aerodynamic Ceiling
Mass
1.3 g Buffet Margin
CG
Step Climb
