BAK Questions Thread

[Romeo Juliet Whiskey]

The BAK question assumes the simple flap full application will always move the centre of pressure of the main wing forward thereby causing a pitch up

But if the centre of pressure is still behind the centre of gravity wouldn't any increase in lift cause the nose to pitch down? If we factor in drag, the nose pitches up (for a jabiru) because the drag moment (pitch up) is great than the lift moment (pitch down)--> net result for the Jab is a pitch up. Does that make any sense? ...lol I can see that all this really is aeroplane specific and this type of question couldn't really be asked in a general context such as BAK.

 

 

[mnewbery]

Complicating things further, the air off a high wing aircraft spills on to the cruciform tail plane more effectively with the flaps deployed.

 

Dash-8 is high wing and T-tail, and on it goes

 

 

[facthunter]

All good comment and shows the best way to pass some exams is to not know too much. An exam should show you know something and can apply that knowledge by making deductions (analyise effects ) correctly from it. Nev

 

 

[Old Koreelah]

...Aircraft that pitch down with full flap application include those with leading edge lift devices (think Boeing 737) and aircraft that use split flaps or a combination of split flaps with fowler action...

...and my Jodel, with flap hinged offset like a Jab.

 

 

[dutchroll]

Aircraft that pitch down with full flap application include those with leading edge lift devices (think Boeing 737)

I'm assuming at this level of BAK that you don't want to factor in fly-by-wire attitude stabilisation which many modern jets with leading edge lift devices have?

 

 

[Parkway]

Bonus point: Name an aircraft that pitches down when flaps are applied.

The sportstar pitches down when you put in flaps. I think it's because it has split flaps rather than normal flaps?

 

 

[mnewbery]

I'll be finding out for myself soon enough. But from what I have read, yes it's because of split flaps. Probably the word normal might be replaced by "simple". I'm backing away from the idea of a "normal" flap

 

 

[Parkway]

I'll be finding out for myself soon enough. But from what I have read, yes it's because of split flaps. Probably the word normal might be replaced by "simple". I'm backing away from the idea of a "normal" flap

Haha yeah I wasn't sure the proper name for what I meant. They're called plain flaps

 

 

[mnewbery]

Is Pearo still calling BS on the fuel vapour?

 

GA News - Why a bonding cable is so important when refueling your plane

 

 

[facthunter]

I think the one that slides out a bit and has extra area plus a slot is called "fowler". This is very effective and used on the Cessna High wing models, giving more extra lift than most GA designs. Nev

 

 

[Romeo Juliet Whiskey]

Another couple of questions from the syllabus I can't seem to find the answer to in my books.

 

i) State why the aeroplane tends to overbank in a level and climbing turn and not in descending turns. The standard answer is: 'the outer wing is travelling at a faster speed, more lift and thus roll. In a descending turn this rolling effect is somewhat cancelled out by the higher AOA of the inner wing'. My question is wouldn't the inner wing also have a higher AoA in the climbing turn, and therefore reducing the rolling affect caused by the faster outer wing and not causing overbanking tendencies?

 

ii) State the effect of aileron drag on the turning performance at low speed. I'm aware of adverse yaw created by drag of the downward aileron but not sure how this equates to turning performance? I thought turn performance at a particular speed just depended on available 'g'. Not sure exactly what they are looking for with the statement in bold.

 

 

[Parkway]

Another couple of questions from the syllabus I can't seem to find the answer to in my books

Have you looked through the stuff on this site? Hit menu at the top left then tutorials

 

 

[Romeo Juliet Whiskey]

Have you looked through the stuff on this site? Hit menu at the top left then tutorials

But for a while... But I might have another look. Thanks Parkway.

 

 

[facthunter]

The "climbing & descending" turns thing is AoA related. Consider imaginary helical springs at each wing tip and you may be able to picture it better. The "extra" speed of the outer wing is very over estimated. In a full 360 degree turn the outer wing tip only goes 3X (approx.) the wingspan further than the inner. In a really steep turn it's even less. In % terms BU$$er all. The most important thing in a turn is the slip indicator, as relates to what the wings will do as far as lifting (equally) goes Nev