FAA TCDS says,

PC-12
Max. maneuvering design speed Va 170 kts (all speeds EAS)
Max. maneuvering operating speed Vo 154 kts at 4100 kg (9039 lbs)
Vo 136 kts at 3200 kg (7060 lbs)
Vo 123 kts at 2600 kg (5730 lbs)

PC-12/45
Max. maneuvering operating speed Vo 161 kts at 4500 kg

PC-12/47 and PC-12/47E
Max. maneuvering operating speed Vo 163 kts at 4740 kg (10450 lbs)

As I understand it, Vo has the same import as Va, and is calculated in the same manner ie full control deflection at that speed will result in a stall while producing the limit load factor. It looks as though PC put a Va on the early aircraft with an eye to weight increases in the future - note they refer to the Va as the design Va. You can see the Vo in the 47 and 47E at 163 knots, edging up towards the design Va of 170, a further weight increase in the offing?

Worrying points bolded.

Read here of a chap who exceeded his aircrafts 3 g limit load by .37 g. Thats 3.37 g he pulled, a long way to go to the ultimate load of 4.5 g, one guy lost his life and a very, very expensive aircraft written off. http://dspace.dsto.defence.gov.au/ds...-0008%20PR.pdf

The 210 is designed to a limit load factor of 3.8 g (normal category) which means its ultimate load factor is 5.7 g. The 50% safety factor is intended to cover variations in material, load assumptions and construction. It is not intended to cover the case of pilots pushing their luck. Even though the airframe is required to support the ultimate load without failure (but only for 3 seconds, after that the whole shebang can disintegrate), the structure may incur permanent damage (popped rivets, broken ribs, permanent deformation) any time the load exceeds the limit load.

You don’t know what sets a particular limit, Boeing says the Vne limit on the B-17 was set by the strength of the engine cowling attachments. Strength of windscreen may set the limit for all we know on a particular aircraft.

It's a scary scenario, the pilot who routinely exceeds limitations, feeling entitled to take advantage of safety factors used in the design. Because the aircraft hasn’t shown any signs of imminent disintegration, obviously its over designed, right? Unfortunately the airframe may be damaged in a way that escapes notice, and imposing large repetitive loads increases the risk of failure. Metal “remembers” the loads imposed on it and is susceptible to the cumulative effects of repeated high loads. Fatigue failures can occur at loads well below that required to break a structure in a single application. Any time a load is imposed the structure is deformed to a greater or lesser degree. Take airspeed and structural limitations seriously.

An example is a RAAF Bristol Freighter near Adelaide 1953, which shed a wing with the loss of all on board. Later found that a previous crew had subjected the aircraft to loads for which it was not designed ie in excess of the limit load. Presumably the accident crew found no deformation or anything untoward on their pre-flight, else they would not have gone aviating.

Hey Wal,
You didn't mind the 4 bolts on the LJ holding the wing on:).We won't even go down the DH104 path:eek: My bird says 270/.7, very vague when you are sittin high, just cant do it. I guess at the onset of turb,unless your AFM or Ops manual differentiates the levels of turb, thats what you gotta do:)Common sense I would hope prevails:ok:

Cheers Brian, interesting stuff. I only ever flew the /45 and didn't know that the straight -12 had a Va.

Thanks Brian,
Aerohooligans post didn't sit right with me but I figured someone who knew more about design /testing etc would point out the bits that were a bit.....borderline stupid.
Aerohooligan , I understand you used a caveat at the end of your post but some folk (maybe less experienced than yourself) will take the info you put up here and run with it like it's the law, when in reality I don't think you understand how g and speed limits are derived yourself.
GA aircraft do break up in flight. Normally in heavy weather. Is that because the pilot was irresponsibly pulling high g at the time or because of long term fatigue of the frame caused by tens of thousands of lower g stresses? I don't know the answer, probably a combo. I do remember bouncing around in tropical weather in C210's wondering how many more years of this the a/c could withstand. Cheers, Framer.

Good to see this thread still 'bouncing' along here:)

What amazes me a little here though is a fair amount of ref is to the G loading of a particluar A/C. 3.5 g's, 4.2 g's for Eg, fair enough there is a limit to everything but what's the point of it all if we as pilots in most common GA A/C haven't got any way of knowing what G we are experiencing in the first place. I guess if the wings fall off then you found that ultimate 'G'.:}
So my original Q still stands, what constitutes (diff words this time) turb enough to reduce the airspeed? It's really only a personal assesment I believe, all the 'g' factors listed,all the kings horses & all the kings men couldn't put the "sh1t out of luck pilot" back together again:E
Been fun riding the roller coaster of late in ML, TS's everywhere:sad:Times like this I wish I was a truckie on 'no-doze':E


Wmk2

p.s.................fancy flying around in a PC12 worrying about turb speed, that's the least of yr worries:E

Too true Wal, and there was a Aero Commander just north of your work place not too long ago that couldn't be put back together again. You would have greater insight than I surrounding the accident.

Interesting that in the latest "Flightsafety" mag they have an item on ageing aircraft and Cessna in particular get a mention. Quote "the wing spars of some popular Cessna models corrode - sometimes badly - but they do so from the inside out. Since there are no inspection holes in the area, by the time anything's visible - from the outside - the wing may already be seriously weakened. Most LAMEs won't know that, because there is nothing about it in the Cessna maintenance manuals."

Aerohooligan, I was going to say go stoke up that 15,000 hour 210, rack the needle past the Vne and pull limit load. You said you had more sense than to do it, but I hope you now see that your be aware that these limits are conservative and do not always represent the absolute physical limits is very, very poor advice in the extreme. You're only 21 so you have a lot of living and learning to do yet. But heh, we're all here to learn. :ok:

Could not agree more, 300series. I don't have a lot of experience so I hope I didn't come across as a know-it-all.

I did my training on aircraft with a MINIMUM of 11,000hrs on the airframe and the oldest had just short of 18,000. I just thought it was interesting that aircraft limits are apparently fairly conservative when the plane is new.

I guess the manufacturer must consider the anticipated service life of the A/C when setting such limits?

BA, sorry that I sounded the least bit cowboy. I really hate quoting material like that because I can tend to sound irresponsible if I don't pick my words extremely carefully. ;)

I want you and all here to know that I have never exceeded airspeed or load factor limitations in an aircraft, let alone 'routinely'. To be honest the thought of doing so under any circumstances scares the **** out of me. I have established a personal SOP that states except in an emergency I will never pull more than 2.0-2.5G in a normal category aircraft. := For any flight which may exceed those limitations (ie a private joy flight) I make sure I am flying an aerobatic aircraft.

I am not hugely experienced, for which I try to compensate by reading lots, having very conservative personal SOPs and trying to learn as much as I can from everyone I meet and talk to in the know.

Please feel free to PM me or reply on this post with the information you have on how such limitations are derived, I'd be really interested to know more. I was pretty much paraphrasing the most interesting points of the article I read.

Framer...

massive my bad. I entirely forgot to consider that metal fatigue is cumulative. Thanks man. :O

Wally, I try to stay out of the yellow arc, and if the bumps are uncomfortable for me - I back it off to Va for the weight.

I was flying a C210 around western Qld when one lost a wing on descent into Cloncurry - so its something that I have paid a bit of attention to over the years, though four years of flying in NZ adjusted my turbulence sensors!

Dr :8

VANS RV AIRCRAFT

If you own an RV, or fly one, checkout what's said about exceeding design speeds at Van's Aircraft - Total Performance RV Kitplanes and locate 'bigger engines' in the performance numbers for each model. It's sobering.

happy days,

AeroH,
One of the best attributes you can have in this industry is the ability to put your hand up and take responsibility when things don't go quite to plan, like you just did. Not bad for a 21 yr old mate. Nice work.
As far as deciding when to slow to turb speed, I do it if it's too bumpy to drink my coffee....seriously.

To be honest, probably the thing that scares me the most is that I'll go out one day to do a session of steep turns, and not come back because some clown has been fooling around or f:mad:ed up some other way, overstressed the plane and decided not to tell anyone in order to cover their ass.:uhoh:

As far as turb, that's a hard one Wal! I know when I slow down, but it's a bit hard to quantify. :}

coffee man coffee....it's the best turb monitor.

Am enjoying the responses here, thanks Guys, a good debate for sure.

Brian I along with many others knew SK (one of two whom had their lives cut short in the AC50 crash Nth of ML) very well. I wasn't flying that particular night but I believe it was very rough down low (BLW 8000 ft)
I guess when turb is severe all one can do is slow to the suggested turb speed & let the A/C go with the flow rather than fight it. Everything has a limit, but where & what is it? That's the $64 Mill Q. I can recall some years ago that when I was driving a light jet over NZ sth Is that I had to ask for a block Alt clearance purely 'cause I couldn't keep the beast at any particular level due severe turb. The auto pilot said..............ya gotta be joking mate!:sad:
Now during my pre-flight (daily) I check the upper surface of the wings to see if I can spot any deformalities 'cause the old Beech rides rough air like a Mack truck & being a "T" tail I shudder to think....One of the old girls has 20000 ldgs now, one day it's gunna snap in two whilst ldg, only hope there's grass under me bum when it does:E

'Dr' in my early green days of flying I was sh1t scared of that yellow arc on the lighties, & the red meant dead to me!

For now if in doubt hang 'em out (the 'dunlops'):ok:


Wmk2

Framer, I agree. I know what the AIP says about it, but coffee is realistically prob the best indicator you've got IMHO of the severity of turb. :ok:

PS thankyou for your kind words.

The only problem with the coffee is if I haven't got one going at the onset of turbulence I have to ding the girls and sometimes it's so bumpy they can't make me one...in that scenario I speed up to get through it quickly.:eek:
I've done a couple thousand hours around NZ but the only time I've had to get a block clearance cause I couldn't hold a height was in Aus!

Thats a very good point, it may seem obvious to pilots with a bit of experience but if you are having your first encounters with turbulence (300hrCPL up north etc) then don't try to fight it as you will only load the thing up more and increase your chances of over stressing it.Roll with the punches.
This is a good thread for learning.

The whole "don't fight it" thing made me think about the protection afforded at Va. If my memory serves me correctly Va only means the a/c will stall prior to (or at) it's g limit if you are at Va. Am I right in saying that at Va you could apply full elevator and the stall would protect the a/c but if you did the same with aileron then all bets are off? If thats correct it backs up the ides of not fighting it. ie if you were in a down draft and applied back stick to maintain height and then got a roll which you also countered with aileron you could exceed the load limits prior to stalling as you are loading the wings up with the roll as well as the pitch.

G'Day 'Wal',

"I guess when turb is severe all one can do is slow to the suggested turb speed & let the A/C go with the flow rather than fight it."

Early '80's.....
Coming back from 'Warbo' to Kal one HOT summer's day in trusty ole' 210, did encounter the BIGGEST line of CB's seen around for looong time.
Was at A100, cruising and noticed the turb / outflow of the smoke from the recently started spinifex fire - all the smoke was going horizontal in all directions from the downdraught.

Picked a 'gap', pulled back to 90IAS, dropped the gear - to maybe 'slow me down a bit' just in case - and let the wonderful beautiful machine (Because she still flies...in Broome) - 'waffle' through, up a bit, up/down mucho/down a lot! - and eventually come out the other side at around 4,000ft.
(Hats and bags on the floor under the seats - do not stand up - intentionally anyway!)
Was 'relatively gentle' in the end.
Powered back up to A100 and came on home. Wot a 'learning experience'....

Told the 'gingerbeers' about it when we got home so they could have a 'look'.

All OK - but never did like going near that Yellow arc in more bumps than would cause the coffee to jump out of the cup....
Probably 'psycho' not really being able to see struts or any other 'visible means of support', and had heard about the one in Qld. vs the Cb......

Cheers:ok:

Very insightful question framer, at Va you can move any control to its stops without harming anything, but it does not mean control reversals or in combination. Control reversal was why the fin fell of the Airbus in New York. In one aircraft I flew the manual stipulated when pulling g while rolling the limit was two thirds of the limit load. The limit load was 6 g being a military aerobatic trainer so pulling g while rolling made 4 g your limit - we had a g meter. Will see if I can dig up info on why rolling g limits what you can pull. And yes at Va pulling g the aircraft will stall and be at the limit load simultaneously. The idea is that if you hit a gust of sufficient intensity the aircraft will stall and not exceed the limit load when at Va.