G loading ?

[Aerodynamisist]

If you are flying straight and level and hit turbulence the aircraft the aircraft gets accelerated to say 2g for a few seconds.

If you are carrying out an aerobatic manoeuvre at say 4g and hit the same pocket of turbulence that had you at 2g straight and level, will you now be accelerated to 6g or 8g ?

[Horatio Leafblower]

I thought G-loading was what made young women's jeans sit halfway down their hips and it was only the G-string that held them up... ?

...or have I got that wrong?

[Giles Tuwotu]

Very unlikely that turbulance would be experienced for "a few seconds"... most turb acceleration (g) only last a fraction of a second!!

[djpil]

Roughly, increase in g results from gusts at right angles to the flight path so in straight and level an increase in g results from a vertical gust. Answer is yes if pulling that 4 g while flying horizontally.
Doesn't matter how short a time, the extra g can break something.

[ops_guy]

I think the question could be read a couple of ways. Here's my take on and corresponding answer for it:

Smooth Air Straight and Level : 1G
Turbulent Air Striaght and Level (oxymoron?) 1G + 1G = 2G

So, the turbulence is actually adding an additional 1G to the normal straight and level G-Loading.

Therefore, if we were pulling in to a manoeuvre with a 4G load and experienced the original turbulence we'd have: 4G + 1G = 5G

Hope this helps

[djpil]

Yes ops_guy, I was never very good at arithmetic.

[Obidiah]

There is more to this, and the formula used takes into consideration;

• The lift curve slope - plan form aspect ratio
• Air density - increased TAS reduces effective gust angle, < R/angles
• Wing loading - A/C ability to react to the gust
• Other things - leading edge radius, IAS

If the scenario were pulling out of a dive at 4g the effective wing loading is 4 times at this moment. Therefore the same gust would create less vertical deflection of the flight path and the pilot/g meter would sense lower g increase than for a lower wing loading. However the bending moment on the wings would still exist commensurate with the lift curve slope, ie strong slope for high aspect ratio and lesser slope for delta form.

So perhaps when at 4g and you encounter the previous gust that created a 2g increase, in this circumstance it may be slightly less, 4+ 1.5g for example.

For the long and complex answer see pg. 332 of Naval Aviators.

Good question.

[Aerodynamisist]

That makes sense Obidiah. hence the higher Turbulence penetration speeds at higher weights on many aircraft.

[Sunfish]

And if I am inverted in the middle of a loop? Or inverted in a barrel roll? DjPl? Mr. Robson?

[T28D]

At the speed you would be inverted in a loop or barrel roll the ability to get an overstress through "G" is impossible.

Maybe a bit of real aerobatics instruction would be a good idea.

[Obidiah]

And if I am inverted in the middle of a loop? Or inverted in a barrel roll?

Dunno....wake up and gets some clean dry sheets.....

Sorry, couldn't resist.

[Obidiah]

Aerodynamisist

hence the higher Turbulence penetration speeds at higher weights on many aircraft.

All aircraft.

Manoeuvre/turb speed = stall speed x the square root of the limit load factor.

[Old Akro]

Turbulence comes from moving through different parcels of air. Aerobatics takes place in a relatively small volume of air (1km x 1km x 2,000ft), so its less likely to involve turbulence from moving through different air parcels. Often a sequence will be done over a single paddock. T28D also reminds that a large amount of the time aerobatics is done at low speed.

A long cruise descent poses the biggest risk from turbulence.

[Sunfish]

T28D:

At the speed you would be inverted in a loop or barrel roll the ability to get an overstress through "G" is impossible.

Maybe a bit of real aerobatics instruction would be a good idea.

1. Don't EVER challenge the Sunfish ability to do something impossibly stupid and break an aircraft.

2, I don't need more encouragement to do aerobatic instruction. I love it. Its addicitive. I just need more time and opportunity to finish the endorsement/rating.

Merry Christmas to all.

[MakeItHappenCaptain]

And on that topic, here's today's challenge.

Is aerobatics/acrobatics performed under an endorsement or a rating?

References please, & no "I was told" or "I thought" answers permitted.

[djpil]

Sunfish, if you are inverted at the top of something then consider that, as some-one else mentioned, you won't break anything at low speed so what's the worst that can happen? Just like "normal" flying. Not pleasant anyway.
If you have the inclination then I have the time to finish your ... whatever it is.

[Ultralights]

whats the worse that can happen?

G Stall just as your in the middle of a roll off the top. damn, rolling G..

[Aerodynamisist]

Endorsement

I don't have a reference for you though, I read the rule book but didn't memorise the page numbers.

[Steve888]

'Tis an endorsement.

CAO 40.0 Subsection 2
2.2 The holder of an aeroplane pilot licence must not, while flying an aeroplane as
pilot in command, or co-pilot, deliberately put the aeroplane into an upright
spin unless:
(a) an authorised flight instructor who gave the holder spinning training is
satisfied that the holder can safely recover an aeroplane from a fully
developed upright spin; and
(b) the instructor has made an entry to that effect in the holder’s personal log
book

2.4 Subject to paragraph 2.5, the holder of an aeroplane pilot licence must not,
while flying an aeroplane as pilot in command, carry out acrobatic flight
unless:
(a) an entry mentioned in subparagraph 2.2 (b) has been made in the holder’s
personal log book; and
(b) an authorised flight instructor, or an approved person, who gave the
holder training in acrobatic flight is satisfied the holder can safely carry
out acrobatic flight; and
(c) the instructor, or person, has made an entry to that effect in the holder’s
personal log book; and
(d) an entry mentioned in subparagraph 2.5 (g) has been made in the holder’s
personal log book in relation to each manoeuvre mentioned in paragraph 2.5.

2.5 The holder of an aeroplane pilot licence may carry out:
(a) a barrel roll; or
(b) a loop; or
(c) a slow roll; or
(d) a roll off the top; or
(e) a stall turn;
if an authorised flight instructor, or an approved person, who gave the holder
flying training in the manoeuvre:
(f) is satisfied that the holder can safely perform the manoeuvre; and
(g) makes an entry to that effect in the holder’s personal log book.
Note If a pilot is approved to carry out more than 1 of these manoeuvres, he or she may carry
out combinations of those manoeuvres

[djpil]

Interesting that the note changed in recent years. If one has loop and slow roll in the logbook then a roll off the top can be performed without a specific logbook entry for it.