Ask The Pilot

[VPS]

Buckingham: Aircraft hit vehicle on road during landing attempt

Its landing gear struck an "articulated vehicle" because its altitude was too low, a report says.

www.bbc.co.uk

I'm glad I wasn't in the lorry - it must have been a bit scary

 

[jb747]

Actually at 0g, the airfoil is not generating lift. That must mean the AoA is zero. (Symmetrical airfoil??) When AoA is zero, the airfoil is always below the stalling AoA and cannot stall.

Induced drag is therefore zero because the airfoil is not generating lift at 0g

Useful if you ever try to leave a dogfight. 0g will give better acceleration than a 1g dive.

 

[jb747]

The basics of their misfortune were decided in advance.

And what, exactly, do you mean by this?

 

[Quickstatus]

1g dive.

What's a 1g dive?

0g will give better acceleration

Is it easy to sustain 0G assuming there is altitude?

 

[jb747]

What's a 1g dive?

Any dive of the sort that you've experienced. Basically a dive with a stable pitch attitude, so -10º, or -30º, but with pilot pitch inputs to hold it at that attitude.

Is it easy to sustain 0G assuming there is altitude?

You have to keep pushing, so the pitch attitude is constantly getting lower. I guess it would describe a parabolic shape.

As a experiment I once rolled and pulled an A-4 to -90º and held it there. Idle and full speed brakes. Started at about 40,000' and as slow as I could go. It actually reached its terminal velocity, and I was hanging forward in the straps. I forget the exact speed it stabilised at, but it wasn't all that fast...400 IAS or so.

 

[Quickstatus]

Any dive

Ok thanks.
More like a 1g descent. I wouldn't call it a dive which is the -90deg nor want to experience one..

I like the feeling of the reaction force pushing up against gravity.

 

[ausfox]

Only been there in aeros.

 

[straitman]

Ok thanks.
More like a 1g descent. I wouldn't call it a dive which is the -90deg nor want to experience one..

I like the feeling of the reaction force pushing up against gravity.

A dive can be a lot less than 90 deg straight down. 20 deg nose down is a shallow dive and still 1G.

 

[Quickstatus]

shallow dive and still 1G.

Understand

It's just my own personal definition of a dive is more vertical. and approaching 0g

 

[justinbrett]

Understand

It's just my own personal definition of a dive is more vertical. and approaching 0g

I think that's just falling. That's what helicopters do.

 

[jb747]

Understand

It's just my own personal definition of a dive is more vertical. and approaching 0g

In airliners, you've probably never experienced more than about -5º. Most descents are at around 0º pitch. Aerobatics lets you pass through many attitudes, but you rarely hold one for any length of time.

Going back to the A-4 stone age, we used three different angles for various weapon releases. 10º for strafing and retarded bombs, 20º and 45º for rockets and normal bombs. The sink rate on the nice shallow 10º was just under 8,000 feet per minute. 20º was 15,000 fpm, and 45º was a heart stopping 32,000 fpm. These were initiated at 2,000', 4,500' and 9,000' respectively. And the ground got very big, very fast. Extra fun at night!

 

[Quickstatus]

32,000 fpm

That's what I mean.
I don't need to confirm Einstein's equivalence principle - a body in a freefall does not have any forces acting on it.

At the bottom of the 45º divebombing run,
How many g would you have been experiencing in the pull-up?

 

[jb747]

At the bottom of the 45º dive bombing run,
How many g would you have been experiencing in the pull-up?

All of the recoveries were similar. About a 6g pull, until you achieved about 30º nose up, then roll to about 70º of bank, whilst holding the g, to turn through around 90 degrees. The turn was important because there was quite a bit of ricochet action from both the 20mm cannons and the rockets.

 

[Quickstatus]

The turn was important

Ah, I thought it was just a "non specific" fly off manoeuvre.

 

[jb747]

Ah, I thought it was just a "non specific" fly off manoeuvre.

I know of one RAAF bloke who managed to shoot himself down (he was actually one of my students at Pt Cook, but I doubt that we covered gunnery). A navy bloke took a hit from part of a rocket, but it didn't do too much harm, other than to his undies.

 

[The black sheep]

Hey there JB747, from what I have read, the airline is not shy to max out passengers and baggage, etc. Hence my post was on the suspicion that they may have been overloaded, so the problems encountered were set up before the actual flight.

And apologies for offerring an armchair opinion what is clear to me now as a "pilots" thread. I was just engaging in the thread, but realize that it is an inappropriate place for me to voice my arm chair opinions You are clearly a pilot, so will follow this with interest, but hold my tongue

And what, exactly, do you mean by this?

 

[Quickstatus]

...Wake turbulence tends to descend behind the airfoil.

I'm thinking simplistically an application of Newton's third law: a force has a equal and opposite reaction.
The force generating lift must have an equal force deflecting air in a downward direction.
Your Thoughts appreciated on this...

Is induced drag highest at wingtips?

 

[AviatorInsight]

Is induced drag highest at wingtips?

Yes it is. It is also highest at slow speeds due to the higher AoA and the wing producing more lift.

 

[RooFlyer]

If the engine is in fact shut down, we still pull both reversers on landing. They’re hydraulically operated. The sleeve will still open and you’ll get idle reverse as opposed to full reverse on the other engine.

Good job from the crew in any case.

( This from the QF engine shut-down thread)

In this case is there any impact on steering as the aircraft slows?

 

[AviatorInsight]

( This from the QF engine shut-down thread)

In this case is there any impact on steering as the aircraft slows?

Slight, but easily manageable even with a crosswind (which they always use in a sim). The 737 has a big rudder and 7° of nose wheel steering when it becomes ineffective which is still good enough to keep it straight on centreline.