Limitations Flashcards
What safety factor is added to aircraft structure
1.5 time stronger than the expected maximum load
What is the minimum load limit (design load limit) of modern transport aircraft
2.5
What is the minimum load limit (design load limit) of utility aircraft
4.4
What is the minimum load limit (design load limit) of aerobatic aircraft
6
How well must a aircraft withstand the load limit
Without damage or bending
What is the ultimate load limit
1.5 x DLL
What is the ultimate load limit for transport aircraft
3.75
What is the ultimate load limit for utility aircraft
6.6
What is the ultimate load limit for aerobatic aircraft
9
How well does a aircraft need to withstand the ultimate load limit
Bending /overstressing is allowed but not breaking / causing permanent damage
How does mass affect load factor
It doesn’t, just a ratio of lift times weight
What are the minimum load limits for a transport aircraft
- 5
- 1
What is the minimum ultimate load factor for transport aircraft
- 75
- 1.5
How does load factor affect stall speed
Higher load factor = higher stall speed
What is Va
Designed manoeuvre speed
Tends to be slightly less than 2.5g stall speed
As long as u are below this speed you won’t overstress the aircraft
What is Vb
Speed for max gust intensity
Must be able to withstand gust of 66ft/ second up or down @ 20,000ft
38ft / second up / down @ 50,000ft
What is Vfe
Max speed for flap extension
How does mass affect Va
Mass up = stall speed up = Va up
How does flaps affect Va speed
Can’t go as fast = smaller envelope = reduces stall speed = reduces Va
What is Vra (Vturb)
Turbulent penetration speed
What is Vc
Design cruise speed
Max speed you can go in cruise before overstressing aircraft
What is Vmo
Maximum operating speeds
Max speed that must not be intentionally exceeded during any phase of flight
What is Vne
Velocity never exceed
For little planes
What is Vd
Design dive speed (design death speed)
Fastest you can go in a dive without breaking aircraft
Gust intensity requirement of 25ft / second @ 20,000
What is Mmo
Max operating Mach number
At higher alt Mmo becomes restrictive and then replaces Vmo as the max limiting speed reference
What is Vno
Max structural cruise speed
Applicable to small aircraft
Slow end of yellow arc
What is Vle
Max landing gear extended speed
Max speed at which the aeroplane can be flown with gear down and locked
What is Vlo
Max landing gear operating speed
Although Vlo May be the same as Vle it is usually slower because gear doors are not properly braced when traveling
What affect does a downgust have on lift
Less AOA
Less lift
What effect does a up guest have on lift
More AOA
More lift
What affect does up and down gusts have on load factors
Up gust = higher load factor
Down gust = Lower Load factor
How does a gust change load factor
Gusts cause change in load factor due to change in lift due to change in Cl due to a change in AOA
How does altitude affect load factor change due to gusts
Less change in AOA therefor less load factor change
How does speed affect the change in load factor due to a gust
Faster speed = greater increase in load factor
How does aspect ratio affect the change in Load factor for a gust
High aspect ratio = high change in load factor
How does weight affect change in load factor due to gust
Proportionally
Heavy = less change in load factor
How does manoeuvring affect the change in load factor due to gust
Less affect
The harder you make the wing work the less gust load effect
What is the shape of the gust load envelope from 1g
Symmetrical
What is the shape of the manoeuvre envelope
Not symmetrical
What is flutter
Gust = increase AOA = twist round flexural axis = once gust removed = wing springs back = bends down = keeps repeating = getting worse
How can you resist flutter
Make wing stronger
Mass balance infront of flexural axis (engine)
Can move flexural axis forward
Sweep back wing
How do control surfaces affect flutter
Gust striking aileron / movement of aileron = makes it worse
What is low speed aileron reversal
Slow flight
Wing at high AOA
Left aileron down (to roll right)
AOA increases
Stall
Roll left
What is high speed aileron reversal
Aileron down at high speed
Up force
Twists round flextorial axis
Leading edge down
Wing = negative AOA
High speed aileron reversal
What wing is high speed aileron reversal worse
Straight wing
What affect does a rearward movement of CG have on downwash
Reduces downwash
What affects Va
Mass and pressure altitude