Arrow PA-28 Experienced In-Flight Break-Up

[englishal]

Look at it this way...

If your aeroplane has a design load factor of 3.8g in one axis, when carrying out a rolling manouvre (e.g. two axis.....a botched barrel roll for example) this HALVES to 1.7g !!!

Something I never knew until it was explained by my aero's instructor....

[marcotiloca]

Another old Pa-28 involved in similar accident...

Hello, Mates!

Here's a series of links in which another old Pa-28 accident is under investigation by the NTSB, in Texas, it is possible it has suffered an in-flight break-up, at least it should seem so, according to what eye-witnesses said...

News on local tv: http://cbs11tv.com/local/local_story_320000519.html

Other news on local press websites:

http://www.star-telegram.com/news/story/305594.html

http://www.dallasnews.com/sharedcont...e.2bb9edf.html

http://www.msnbc.msn.com/id/21827539

A couple of pictures of the plane involved:

http://www.skymates.com/fleet/images...307-05-072.jpg

http://www.skymates.com/fleet/N55307.htm

Weather conditions at the time of the accident from NOAA:

http://www.weather.gov/data/obhistory/KABI.html

NTSB pages of last reports of the month:

http://www.ntsb.gov/ntsb/AccList.asp?month=11&year=2007

My condolences to the family and friends of those pilots and passenger who died in the wreckage...

Marco

[deice]

Holy cow!

[Yankee]

Most common types have suffered in flight breakups. A few (very few) types haven't. The Socatas have a single piece aluminium spar, machined from a solid lump.

Well how does the Grumman AA5 fair up in this debate. No none in flight structure failures.
How does 15G sound. Quote from a recent forum question on the Grumman Gang

Except for the Grumman, most wing structures rely on a forward and rear "I"
beam spar with both spars interconnected to the fuselage structure and then
relying on the skin of the wing to keep the spars perpendicular to the air
loads. The sheet metal "I" beam looses it's strength if twisted slightly.
The main reason so many strutless Cessna 210s have lost wings is the skin
wrinkles between the spars twisting the rear spar causing it to fail.
Grumman's rely on a massive tube that can withstand loads equally in ALL
DIRECTIONS. There is a rear spar but it ends at the wing root and is not
attached to the fuselage, therefore all flight and accident loads are
transmitted into the center spar without reliance on skin structure. Air
loads go from the skin, to ribs, to spar collars, to one spar, to fuselage,
similar to some rag wing airplanes.
Hypothetically if you were to saw a Grumman wing in 1/2 at the root without
touching the center spar it would have almost the same strength as before.
Can't do that to any of the brand X without the wing flexing all over.
Remove a Piper leading edge fuel tank and that wing becomes very flexible.
Disadvantages of a tube spar are that it theoretically doesn't give a much
strength per pound of aluminum.
Advantages are it will withstand G loads with or without twisting loads,
incredibly hard impacts with hangers, tugs, etc. without buckling the rear
spar as with other aircraft. Damage is usually limited to the skins.
Exceeding the "G" limits will buckle or compress the upper spar surfaces and
stretch the lower surfaces. So far those "Gs" have been less then 15 or so
in flight. I have seen an extra 12" dihedral in the wings and anhedral in
the horizontal stabilizer "15G" load according to Gulfstream Aerospace. I
have two buckled outboard wing panels here that withstood a loaded DC-10
wake turbulence that was so violent it sheared both 1/2" chrome molly steel
aileron counterweight tubes and sent them into an apartment building below.
Both airplanes continued flight without incident.

The above aircraft was not totaled.

Except the wings, the airplane was fine, I trailered it back to Houston from
LA and we inspected the entire airplane especially the spar attach points
and spar, found no damage. We installed a pair of new wings and flew it
back.
David Fletcher

The 15G load incident was not the same as the DC10 wake turbulence incident. Believe that one was an encounter with being sucked up inside a CB and spat out. Wings, spar, horizontal stab and windows had to be replaced in that one, but it did survive. The 15G was what Gulfstream said the spar had been stressed to after putting it though their test rig.

[SNS3Guppy]

I understand the above is on flight load limits, but can we assume that even passing Vne we still have some safety margin ?

NO!!! Absolutely not.

Wing bending moment and load factors are not the primary criteria in determining Vne. Go back and read about flutter again.

There is one more speed after Vne, Vd design speed that is where you are guaranteed that the wings will come off in a dive without any control input at all in still air conditions.

No, absolutely not.

Vd, or Design Dive Speed, is a reference speed, and it's not a cockpit speed you'll read on your airspeed indicator. It's provided as Equivilent airspeed, and it's also not something you'll likely find in the AFM/POH for your airplane. It is NOT the speed at which the wings come off.

Your limitation with respect to maximum speed is Vne. The wings don't separate there either, unless you pull them off, but you still need to religiously respect the limitations for the airplane. Design diving speed is not a limitation. Vne is. Design diving speed is a reference speed upon which certain tests and other criteria is based.

Additionally, the word "design" in the various certification speed terms does not mean that is what the airplane was designed to do, but rather that it's a reference speed for certain certification criteria, for that airplane design, or airframe.

If your aeroplane has a design load factor of 3.8g in one axis, when carrying out a rolling manouvre (e.g. two axis.....a botched barrel roll for example) this HALVES to 1.7g !!!

That's a good guess, but no...it doesn't decrease by any particular percent. There are far too many variables involved. You're correct, however, that additional forces beyond simple loading are involved, as the airplane is also under torsion (twisting), bending, tension, compression, and even shear loads in any maneuver. The interaction of these forces compounds and becomes quite complex in the presence of multiple control inputs and rapidly changing combinations of forces. Even a single control axis with inputs in both directions has already exceded the boundaries established by maneuvering speed...Va. Once you reverse the direction of the controls you've already gone beyond that upon which Va is predicated; a single control input. Compound that further with multiple inputs of the same, or different controls, or any combination thereof, and you're no longer in the same theatre as the stage on which Va was set.

[bjornhall]

So how big is the margin between Vne and Vd in a light aircraft?

[Islander2]

So how big is the margin between Vne and Vd in a light aircraft?

There is no fixed relationship between Vd and Vne.

The minimum value for Vd is a fixed multiple of Vc (the design cruise speed), the multiple depending on the aeroplane's design category (1.4x for normal category, 1.5x for utility category and 1.55x for aerobatic).

It may help, though, to give a specific example.

My A36 Bonanza has Vc=167 kts, Vne=205kts and Vd=250 kts.

In response to observations about Vd by G-EMMA and SNS3Guppy, I would point out that, amongst the various criteria that have to be satisfied at Vd, there is a requirement for the controls to be flutter free and also for the aeroplane to withstand a sharp-edged gust (15fps for compliance with CAR 3)

[sternone]

Hurt ?

I may understand that some of you flying a Warrior don't feel good when they read reports that their favorite bird has come apart in flight without good reason.

For me, it's clear, i know the Warrior isn't as rugged build as a Mooney or a Bonanza, that is clear as crystal. If you look for example to the flaps connection mechanism of a Cirrus plane and compare that to one of the Mooney or Bonanza you know what is going to fail first probably... i like the Mooney and the Bonanza more for this reason, it's just better and stronger build. Period.

[Contacttower]

i like the Mooney and the Bonanza more for this reason, it's just better and stronger build. Period.

Well from now on I'm going to fly around in a Spitfire, now there's an aircraft that won't be suffering in flight break up.

[SNS3Guppy]

Well from now on I'm going to fly around in a Spitfire, now there's an aircraft that won't be suffering in flight break up.

Don't want to burst your bubble or anything, but here's a brief, partial list of a few Spitfires that did...

Mar 39...Mk I....K9838...Structural failure in dive.
Jan 41...Mk I....N3191...Both wings broke off in dive.
Jul 41...Mk I....X4354...Port wing broke off in dive.
Aug 41...Mk I....X4381...Starboard wing broke off in dive.
Mar 41...Mk I....X4421...Both wings broke off in dive pullout.
Jul 41...Mk I....X4662...Stbd wing broke off in dive pullout.
Jun 41...Mk I....X4680...Wings/tail broke off in dive pullout.
Nov 42...Mk I....X4621...Failed to recover from dive.
Apr 43...Mk II...P7352...Broke up in dive.
Sep 41...Mk II...P7522...Both wings broke off in dive.
Jun 43...Mk V....BL531...Both wings broke off in dive.
Feb 42...Mk V....AA876...Disintegrated in dive.
Jul 43...Mk V....BL389...Pilot thrown from aircraft in dive.
Jan 43...Mk IX...BS251...Structural failure in dive.
May 43...Mk IX...BS385...Structural failure in dive.
Aug 43...Mk IX...BS441...Disintegrated in dive.
Oct 46...Mk IX...PL387...Disintegrated in dive.
Jan 48...Mk XVI..SL724...Crashed after recovery from dive.
Sep 48...Mk XVI..TD119...Crashed after recovery from dive.
Aug 42...Mk I....N3284...Broke up in flight.
Aug 41...Mk I....N3286...Broke up in flight.
Sep 40...Mk I....P9546...Structural failure in flight.
May 42...Mk I....P9309...Lost wing in flight.
Apr 43...Mk I....X4234...Lost wing in spin.
Sep 42...Mk I....P9322...Broke up in flight.
Aug 43...Mk I....R6706...Aileron failure which led to crash.
Jan 43...Mk I....X4854...Starboard wing broke off in flight.
Nov 40...Mk II...P7593...Stbd wing and tail broke off in flight.
Dec 41...Mk II...P8183...Port wing broke off in flight.
Jun 42...Mk II...P8644...Starboard wing broke off in flight.
May 41...Mk II...N8245...Structural failure in flight.
Feb 44...Mk II...P7911...Flap failure which led to crash.
Sep 42...Mk V....AD555...Flap failure which led to crash.
Mar 44...Mk V....BL303...Flap failure which led to crash.
Dec 41...Mk V....BL407...Structural failure suspected.
Jun 42...Mk V....AB172...Structural failure in flight.
Mar 43...Mk V....AA970...Structural failure in flight.
Jun 43...Mk V....BL290...Port wing broke off in flight.
May 43...Mk V....BR627...Port wing failed in spin.
Oct 41...Mk IV...AA801...Structural failure in flight.
Feb 43...Mk IX...BS404...Structural failure in spin.
Feb 45...Mk IX...MH349...Wing failed during aerobatics.

(reference Spitfire: The History)

In Spitfire at War, by Alfred Price, Eric Newton is quoted as saying:

"Out of a total of 121 serious or major accidents to Spifires reported to us between the begining of 1941 and the end of the war, 68 involved structural failure in the air. Initially the most common reason for such failures, with 22 instances in 1941 and 1942, was aileron instability. The symptoms were not at all clear cut: the aircraft were usually diving at high speed when they simply fell to pieces. Only after one of the pilots had survived this traumatic experience and parachuted successfully were we able to find the cause. During his dive he saw both of his ailerons suddenly flip up, producing an extremely violent pitch- up which caused the wing to fail and the aircraft to break up. In collaboration with RAE we did a lot of tests and found that aileron up- float was made possible by stretch in the control cables; in those days tensioning was a hit or miss affair with no compensation for temperature. On our recommendation the RAF introduced a tensometer which ensured accurate tensioning of the controls; this, and the simultaneous introduction of metal surfaced ailerons ('42/'43), cured almost all the cases of aileron instability in the Spitfire.

The next most serious cause of structural failure in the Spitfire was pilots overstressing the airframe. She was extremely responsive on the controls and one must remember that in those days there was no accelerometer to tell the pilot how close he was to the limit. So it was not difficult to exceed the aircraft's 10G ultimate stress factor (what was the 109's?- Berkshire) during combat or when pulling out from a high speed dive; during the war we were able to put down 46 major accidents to this cause, though undoubtedly there were many other occasions when it happened and we did not see the wreckage. Incidentally, if there was a structural failure in the Spitfire it was almost inevitably the wing that went; the fuselage was far less likely to fail first (the same for most low wing monoplane fighters?-except the Typhoon?- Berkshire).

I once asked a very senior RAF officer why the accelerometer- technically a simple instrument- was not introduced during the war. He replied that he was sure it would have an adverse effect on the fighting spirit of the pilots (same was said re the parachute in WW1!- Berkshire).

Whether that would have been so I cannot say. But I do know that when they finally introduced the accelerometer into service in the Hunter in 1954, and began educating the pilots on structural limitations and the dangers of overstressing, accidents to this cause virtually ceased.

After structural failure the next largest category of accidents proved on investigation to have followed loss of control by the pilot (36 cases). Of these 20 occured in cloud and could be put down to pilot error; one must remember that in the rush to get pilots operational instrument training was not up to peacetime standards. A further 13 accidents were shown to have been caused by oxygen starvation; the oxygen system had been used incorrectly with the result that the pilot had passed out and the aircraft had crashed. As a result of our investigations the system was modified to make it easier to operate.

The remaining 3 accidents in the loss of control category were initiated by the pilot pulling excessive G and blacking himself out."


Whereas a tough, solidly built tactical airplane designed and stressed for maneuvering and violent aerobatics can experience those failures while being flown by a pilot who is trained and capable above and beyond what the basic private pilot syllabus provides, how much more careful ought one to be with the modest Arrow or 172? Yes indeedy, they all most certainly do break.

[VFE]

Just to give some of you guys an idea of the sort of chap Sternone is, below is a copy of an email I recieved in reply to some friendly advice I offered him:

You know what you stupid **** ? I don't care what your advise is, but if you think that you can just come over here and tell me what to do guess again, you are wrong, and i don't care at all. If a place called a forum isn't allowed to have some guys asking/telling what they wan't then society is clearly a wrong place for you. I think you have absolutely no idea who i am and what i have done in my life, and if i'm low houred and not know it all and must receive such a ridiculus messages from pricks like you it shure makes my day, i just laugh at you dude, go away, you know your ugly and your mom dresses you funny ?

Get a live dude, it's not my fault that you are a proletarian aviation teacher.

Personally, I would think twice about dignifying any of his further postings with a reply. One can only hope he/she merely vents steam through the internet and doesn't present this attitude towards their flying instructor - who, incidentally, has come in from a fair amount of criticism from this young pup on these pages since their registration. My heart bleeds for poor sod who may be presented with this kind of attitude in the course of attempting to instruct.

VFE.

[scooter boy]

PA-28 breakup

Nice list of spits sans wings!

For me it probably boils down to (and I haven't seen any NTSB report yet) the fact that a lot of PA-28s (after Cessans) are used for ab-initio training/self fly hire and take a serious hammering, more expensive types generally do not.

Would be essential to know the history of the aircraft (and whether I had landed it in the past! )

SB

[sternone]

VFE: you should point out that this was in response of your message to me:

Sternone,
A wise man once said: "it is far better to be thought of as stupid than to opens ones mouth and remove all doubt".
My advice to you would be to read more instead of typing. By all means raise an issue but please leave the comment like the one in your opening post because you clearly have very little knowledge so far in your flying career.
Whilst I am giving a lecture, may I also suggest you refrain from posting critisisms of your flying instructro, as is your want, on these pages. You need to wind your neck in a little and listen instead of rabbit. It's called learning.

First of all i sended this message privatly to you because this seems to be something between you and me, but you choose this to make this on the forum, no problem, and secondly i can't help it that you guys fly things that fall apart, also you must understand that if you attack, you can receive counter attack, that is what happend here, enjoy it, hate it, but don't let it spoil your day... just give me facts and i might change my mind

[wombat13]

Sternone, I had reason to pull you up a few months ago for writing utter tosh on this forum. Seems like bullsh!t is in your blood.

The real problem with clowns like you is that a real novice (as opposed to the novice in denial you so obviously are), may for a while take what you write as credible.

You really should consider taking a break from posting for a while - at least until you achieve 25 hours P1 post GST.

In case I did not make myself clear in that last posting to you, you are an idiot.

The Wombat

[sternone]

Sure, do i really look like i care ?

[wombat13]

Another killer response from the idiot we know as Sternone.

[sternone]

Haha, i knew i would have an entertaining sunday morning!! You have to understand that i really read facts, technical stuff on this forum, but just telling a user to p!ss off because he hasn't logged and read enough to your standards may work for some people to shut up, but not for the idiot me!! Live with it!

[PompeyPaul]

Sheesh

Is it any wonder that GA is in such serious decline when we can't even be civil in discussions on an online forum ? Just look at our attitudes to each other, extrapolate what our attitude is to the outside world, and then wonder why places like Lee are closing....

[Cusco]

I, for one, who have flown an Arrow for the last 13 years, will continue to do so with complete confidence until someone with considerably more authority than sternone, such as the FAA or CAA/JAA/EASA, tells me not to...............
Safe flying
Cusco

[Sleeve Wing]

>:entertaining sunday morning!! :<

Time for the Mods ?