Arrow PA-28 Experienced In-Flight Break-Up

[sternone]

NTSB Says PA-28 Arrow Experienced In-Flight Break-Up

Tue, 13 Nov '07

Outboard Wing Sections Broke Off, Ailerons Also Separated

An airplane that went down in southwestern Utah in October, killing two brothers, broke apart in mid-flight, according to the National Transportation Safety Board.
The NTSB has released a preliminary report into the crash that killed Benjamin and James Timpson of Centennial Park, AZ. The single-engine Piper Arrow crashed the evening of October 26 near Colorado City, AZ.
According to the prelim, the airplane was flying from Bountiful, in Davis County, to Colorado City when it experienced an in-flight loss of control, broke up and then crashed into mountainous terrain about 21 miles southeast of Cedar City.
"The airplane was destroyed during the in-flight breakup and post-impact ground fire," the report said. "The entire instrument panel, cockpit and cabin were destroyed by fire, along with several acres of adjacent native vegetation on the mountainside, elevation 6,400 feet mean sea level."
An NTSB investigator examined the crash scene and noted the "outboard portions of both wings separated from the inbound span of the wings, which remained attached to the fuselage."
"The ailerons were found separated from the wings," the report said
The NTSB said recorded air data showed the plane left Bountiful at 6:15 pm on October 29, heading south toward Colorado City's airport.
"Thereafter, the rate of descent increased as the airplane reversed its course. The main wreckage was located about 1/3 mile from the airplane's last radar recorded position," said the preliminary report.

May they RIP... we might not know what happend, but no Arrow plane for me please...

[Kiltie]

Yes, be warned everyone; all Piper Arrows break up in flight, Mooneys of course never do.:rolleyes:

[smarthawke]

Sternone

How about nipping off and getting some experience in the world of GA (flying and time) before posting such ridiculous comments.

Your posts are normally written as one of great knowledge but are normally flawed to those who know a tad more than you. I'm sure if you look you'll find Mooney's and cessnas and all sorts of machines that have suffered structural failure in flight - it doesn't necessarily mean that there is a design flaw or the aircraft is weak.

Perhaps you could go off and find out how many hours have been flown by PA28Rs without having the wings fall off.....

[yawningdog]

I remember reading about another Arrow that broke up within the last few years. The reasons given were that full control movement over stressed the airframe.

Just speculating, but if the weather was poor or IMC around rising ground, its feasible that this recent breakup could have been as a result of over stress due to over control. Ie: disorientation or panic.

Arrows are great aircraft. If there was an inherent structural problem with Arrows, it would be happening all the time as there are so many.

[The Nr Fairy]

yawningdog:

Well remembered. AAIB accident report (PDF) here (http://www.aaib.dft.gov.uk/cms_resources/dft_avsafety_pdf_025533.pdf).

[Contacttower]

we might not know what happend, but no Arrow plane for me please...


Arrows are perfectly safe provided they are operated within their envelopes and maintained to the right standard. But as you have said before (and I agree with you) they are not as solidly built as some aircraft and may once having departed its safe envelope prove more vunerable to inflight break up than say a Beech Bonanza.

Personally I think the PA28 is a great aircraft and has given many years of sterling service to the FTOs of the world. And as someone who has flown nearly all the PA28 models there are and have about 150 hours on them I feel qualified to comment.

[Tony Hirst]

One thought that struck me is the potential for a constant speed retractable gear aircraft to quickly exceed at Vne with the confusion that can follow a nose down unusual attitude. Although possible, the potential is generally substantially less with a fixed prop and fixed gear.

[sternone]

How about nipping off and getting some experience in the world of GA (flying and time) before posting such ridiculous comments.


Besides the fact that i feel sorry for these 2 unfortunatly pilots i would like to ask you, would it have been breaking up when it was a mooney or a beechcraft ? Maybe yes, probably no.

Hihi, Also i feel quit sorry for you that the only argument you can tell me is that i'm low houred not yet PPL rated.. comon, please do better than that, i could actually learn something from you guys.

[BackPacker]

Also i feel quit sorry for you that the only argument you can tell me is that i'm low houred not yet PPL rated.. comon, please do better than that, i could actually learn something from you guys.

Have you done the aircraft performance test yet? Because I think you don't give enough credit to this comment:

The reasons given were that full control movement over stressed the airframe.

All aircraft, without exception, have a Va limit, which depends, to a large extent, on the strength of the wing spar. In fact, in order to certify, the aircraft structure has to be strong enough to survive certain "g"'s at MTOM, and Va is a direct result of that. (For a normal category aircraft, I think the positive g limit is 3.8. Not a lot actually.)

If you fly faster than Va (and Va changes with actual mass) and apply full and abrupt control deflections, you will exceed the design parameters of the airplane. If you also exceed the safety margin that manufacturers built in, then you will break off the wings (or the tail section). Doesn't matter whether the aircraft is built by Mooney or Piper.

If you challenge me, I would be willing to take up a Mooney and demonstrate that it is indeed possible to fly its wings off. Mind you, I'd want to do an emergency egress course and a parachute free fall course first. But then I'd just dive a Mooney to Vne (or beyond) and pull up sharply. (On second thoughts, never mind.)

Edited to add that it's not uncommon to have a Va that is *lower* than the typical cruise speed. So even if you apply full and abrupt control deflections in the cruise, you might break the wings off.

[Mark1234]

i would like to ask you, would it have been breaking up when it was a mooney or a beechcraft ? Maybe yes, probably no

A conclusion reached how?? For my part, I'll say the answer is YES.

There's a design requirement to meet 50% more than design G loadings (so 5.7G) before failure.
[edit to add having flown a very few aeros 4+G is actually rather a lot to most pilots - really, it's not the sort of limit you just creep up on not realising! try it some day :)]

The reported details give no clue as to *why*, however, exceeding those limitations, suggests loss of control in some fashion, however induced (or doing something really daft, but let's leave that).

If out of control, it's most likely that the aircraft would exceed whatever the actual limits of the airframe were, EVEN if there was a little more margin in other types than the arrow - there's nothing to suggest the outcome would be different in any type.

[yawningdog]

Don't worry about that comment sternone, that's the nature of forums.

I think its a good subject to raise, and anyone who hasn't flown much in Arrows might well be put off by an accident like this. But if there is anything to learn from the limited amount of information available here is that, excessive deflection of the controls above or around the max maneuvering speed could cause structural damage in almost any aircraft.

That doesn't mean you should be scared of performing steep maneuvers, you may need to perform some to avoid a collision or something. But be aware that there are limitations.

My understanding of the definition of max maneuvering speed is that full control deflection is not permitted.

[dublinpilot]

If I remember correctly the accident investigators, investigating the UK arrow accident, had to try extremely hard before they could get sufficient g forces to break the wing.

The took the cruise speed (which is above Va on an Arrow) and applied a sudden and abrupt full control deflection, but didn't get anywhere near the needed forces. So they then tried a sudden and abrupt control deflection from one extreem to the opposite, and got nowhere.

So then they tried a sudden and abrupt full control deflection in two axis, and got nowhere. Then they tried a sudden and abrupt full control deflection in two axis from one extreem to the other and got nowhere.

In the end, the only way they could break it was, a sudden and abrupt control deflection from one extreem to the other, in two axis, and then and instant full and sudden reversal back to the opposite extreme.

If you try hard enough you can break an airplane, but the Arrow is by no means an easy aircraft to break.

dp

[deice]

Sternone, I think that you're proving yourself to be perhaps a bit too interested in jumping to quick conclusions without any factual base at all, and unfortunately for you, you're conclusions and ideas are wrong, hence strong words from other posters. If you had elected to say, "this and that happened, would it have made a difference in a Mooney?" instead of offering completely outrageous remarks, then perhaps we would indeed be more inclined to teaching you a thing or two...

VA has been described and I'd like to add that for most aircraft it is indeed lower than cruise speed and many times much lower even. A Malibu for example cruises at 180 knots with a VA at 130 or so. That's a 50 knot spread. Have you checked the Vcruise/VA spread of a Mooney lately? It's about probably even greater as the VA for the M20 is around 130 knots and cruise is upwards of 200 knots.

I wouldn't call myself an experienced PA28 pilot with only about 250 hrs in them myself, but I'm pretty sure you need to pull some massive Gs at high speed to break anything off of them. But it can be done.
Many years ago there was a relatively spectacular crash with a Malibu in Sweden. They popped vertical out of a cloud heading for the ground and likely pulled themselves silly as they managed to break the tail off, which from testing takes a massive 9G load before failing! Piper knows their business no doubt.

[Brooklands]

and may once having departed its safe envelope prove more vunerable to inflight break up than say a Beech Bonanza.

The Bonanza isn't (or wasn't) exempt from in flight break ups. In its early years in V-tail form, it acquired the nickname The fork tailed doctor killer (http://en.wikipedia.org/wiki/Beechcraft_Bonanza) due to a number of in flight breakups.

As others here have said, if you take an aircraft outside its normal opertaing envelope and overstress it, then you shoulnd't be surprised it bits fall off.

Brooklands

[Mark1234]

As an aside, I believe it's far easier to break an aeroplane through overspeed than over-G - if my memory serves, VNE is only 10% less than max flight tested, rather than the 50% on G-loading. I may be thinking about sailplanes though, which I would expect to be more flutter prone than shortwing tin (and have higher G limits).

[IO540]

If you want a plane with no known case of in-flight failure, get a TB20 :)

One thought that struck me is the potential for a constant speed retractable gear aircraft to quickly exceed at Vne with the confusion that can follow a nose down unusual attitude. Although possible, the potential is generally substantially less with a fixed prop and fixed gear.

Not sure I agree re the CS prop bit. A CS prop gives you better pitch stability, because IAS variations (due to pitch changes) do not translate into RPM (and thus fuel flow and thus thrust) changes.

The fixed gear is also a redherring. A slippery airframe will speed up more than a less slippery one. A Lancair is quite slippery despite its fixed gear.

However, this stuff can be well overdone. When I was looking at the TB20, I was still hanging around the flying school scene and the instructors were giving me dire warnings about busting Vne within seconds of pitching down. It's a complete load of b011ocks. The TB20 is a piece of cake to fly and one would have to totally lose it first to hit Vne accidentally, in a spiral dive of some sort. Otherwise, a nose down pitch just makes it speed up and then it wants to climb back again...

I do think the PA28 family isn't particularly sturdy but they aren't designed to be. They are slow plodders, flying mostly at ~ 100kt.

[BackPacker]

having flown a very few aeros 4+G is actually rather a lot to most pilots - really, it's not the sort of limit you just creep up on not realising! try it some day

True. I just finished an aeros course and the first few times I pulled 4g to enter a loop I scared myself to death. But it's becoming routine now. Just to the point where I feel I might be dangerous in a non-aeros plane... :=

Anyway, your comment reminded me about another story, which happened some years after WWII in a DC-3 or something. The captain on this regular commercial flight had flown the same type in the war. On this particular flight it so happened that one of his old war buddies was a passenger, and he was quickly invited into the cockpit for a chat.
While exchanging stories, the passenger quietly slipped the gust lock over the controls - a practical joke they played every now and then in the war on inexperienced flight crews.

When trying to correct a flight path excursion, the pilot would find his controls frozen leading to brief, hilarous moments. Only in this case, the pilot (now operating under a different SOP) did not correct the flight path excursion with the control column, but by adding a little downwards trim. A few seconds later the captain noticed that this did not have the desired effect, so added more trim. And more. And more. The passenger, seeing that his practical joke did not fly, decided at this point in time to remove the gust lock.

The results were horrendous. The aircraft all of a sudden pitched down with something like minus 1 or minus 2 gs. Both the captain and the passenger, which were not properly strapped in, were smashed against the ceiling of the cockpit. In the cabin the result was even more dramatic, with several cabin crew and passengers breaking limbs and getting cut.

The day was saved by the young co-pilot who had remained strapped in properly, and been keeping an eye on his captain. He managed to pull the aircraft out of the dive, reset the trim, adjust the throttles (which, in this particular aircraft, were mounted on the ceiling, where they met the captain on his way up) and get the aircraft back on its proper flightpath.

I don't remember the exact outcome, but I would not be surprised if the aircraft was bent beyond repair in the process anyway. (Wish I had made a bookmark on where the original story can be found...)

Edited to say that Google is your friend... http://www.airlinesafety.com/Unions/Sisto.htm I got some of the details wrong. Oh my. :O

[deice]

I do think the PA28 family isn't particularly sturdy but they aren't designed to be.
I know several mechanics that say the same about the TB, but I account it to their years of Piper/Cessna indoctrination.:E They take a beating from students and survive, so they're not that badly designed. We've had two accidents where the main gear poked through the top skin though so there may be some dinky bits in the design...
I know for a fact that our ex TB10 had its moments but in general was pretty nice. Having said that, the flying Citroen is no match in sturdiness against my ex mount, the Commander 114B. Talk about over engineering!! I believe they had aircraft carrier operations in mind when it was developed.
Is that a GT you're flying IO540?

[wsmempson]

So, just to recap some of the opinions voiced by Sternone on this thread and one or two other recent ones;

1. Piper Arrows are very dangerous because they are renowned for having their wings fall off.

2. DA42's are rubbish because there isn't a P1 armrest, and you have to endure your right arm in your lap.

3. Beech Bonanza's are great for getting in and out of short grass strips.

Those of us who actually fly these machines are learning something new every day.:)

[Fuji Abound]

When trying to correct a flight path excursion, the pilot would find his controls frozen leading to brief, hilarous moments. Only in this case, the pilot (now operating under a different SOP) did not correct the flight path excursion with the control column, but by adding a little downwards trim. A few seconds later the captain noticed that this did not have the desired effect, so added more trim. And more. And more. The passenger, seeing that his practical joke did not fly, decided at this point in time to remove the gust lock.

The results were horrendous. The aircraft all of a sudden pitched down with something like minus 1 or minus 2 gs. Both the captain and the passenger, which were not properly strapped in, were smashed against the ceiling of the cockpit. In the cabin the result was even more dramatic, with several cabin crew and passengers breaking limbs and getting cut.

Cracked me up, anyway.

[IO540]

You can bend or break any plane if you hit something with it. That doesn't mean anything.

The question is how easy it is to bend when flying.

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.

The Commander landing gear is the sturdiest I have ever seen, but it will only be as good as its attachment points. The TB20 is a very similar trailing link setup though not apparently as strong.

Deice- Yes.

Fuji- did you read about that Irish King Air which got bent to the point where upper skin was flaking off, but "nobody noticed"?

[Three Yellows]

And if you are hour building, please fly a real twin, like a Seneca V, Baron, ... not a DA42... i disapprove commercial student pilots learning in FADEC controlled twins...


This was posted on Nov 9th, just one month after his first solo!

Sternone, do you think that, for example all new train drivers should learn on the Flying Scotsman before they are allowed to take out a start of the art Pendelino?

By the way, you don't need an armrest on the DA42 as the autopilot does all the work from about 800ft after take off until about 300ft above the runway (ILS equipped ones anyway). The armrest would get in the way of pouring out the coffee.

What did you solo on by the way?

[ronnie3585]

Fuji- did you read about that Irish King Air which got bent to the point where upper skin was flaking off, but "nobody noticed"?

Elabourate - please?

[wsmempson]

Quote "What did you solo on by the way?"

Concorde, I shouldn't wonder....:hmm:

[englishal]

Any plane can break up in flight, it depends on the noodle at the controls.

Saying that, there was a B747SP which hit severe turbulence over the pacific some time ago. It went out of control and during the recovery they estimated that the pilots pulled > 5G ....they bent the airframe. Still managed to fly it to the USA, several hours away....:eek:

5G is a lot. But that is not the whole story. If I grab the stick and yank it aft (at Va), I may well get away with pulling 5g and surviving to tell the tale. If however, I yank the stick full aft and also wack it over full left or right, the wings may pop off well before we even get near to stalling.......

[SkyHawk-N]

If you want a plane with no known case of in-flight failure, get a TB20

N110U (http://www.ntsb.gov/ntsb/GenPDF.asp?id=LAX04LA251&rpt=fa)?

N163GT (http://www.ntsb.gov/ntsb/GenPDF.asp?id=NYC04LA082&rpt=fa)?

[SkyHawk-N]

cjboy, yes I think you missed the point, try reading the post, no sign of the word 'structural' in IO540s quote.

[421]

Irrelevent. Engine failures are down to the engine manufacturer (Lycoming in this case). Engine failures happen to any aircraft. This thread is specific to in flight break up. IO540 was refering to the fact there has been no case of an inflight break up of a Socata.

[SNS3Guppy]

All aircraft, without exception, have a Va limit, which depends, to a large extent, on the strength of the wing spar. In fact, in order to certify, the aircraft structure has to be strong enough to survive certain "g"'s at MTOM, and Va is a direct result of that. (For a normal category aircraft, I think the positive g limit is 3.8. Not a lot actually.)


Not all aircraft have a Va assigned. Transport category aircraft, for example, don't use Va. Other speeds are used, such as recommended turbulence penetration speeds, though sometimes these are minimumum speeds, and in some cases, maximum.

No, VA doesn't depend on the strength of the spar, but it does have to do with loads on the controls as well as the primary aircraft structure. VA is predicated on stalling before structural damage will occur, and is therefore predicated on on a stall relieving the load before any structural margins are met. Meeting Va also depends on movement at a given rate; more or less than this does not provide protection, and one can indeed break an airplane below Va. Va is also predicated on a single movement of the controls (single event deflection of the control surface), not control reversals or multiple deflections; again, an airplane may break well below Va. It's not the magic number many instructors seem to believe it is.

The G limit of the airplane isn't tied to Va. Maneuvering limits are not the same as the loads imposed by Va, and trying to think of them together only confuses the issue. Certification G load limits are assigned per the aircraft type certification, whereas loads considered for maneuvering speed, turbulence penetration speed, and other such speeds (which can vary depending on aircraft configuration and weight) are design limits. One discusses where you can go legally and *safely,* whereas the other discusses where things will start to break. Two different subjects.

Ever wonder why maneuvering speed varies with weight? It's a stall margin...stall at higher airspeeds at higher weights, and maneuvering speed increases accordingly. Again, you can overstress an airplane below maneuvering speed.

A good example of that is American Airlines Flight 587, which experienced a separation of the vertical stabilizer owing to multiple control inputs by the pilot at a relatively low speed during climb.

If you fly faster than Va (and Va changes with actual mass) and apply full and abrupt control deflections, you will exceed the design parameters of the airplane. If you also exceed the safety margin that manufacturers built in, then you will break off the wings (or the tail section). Doesn't matter whether the aircraft is built by Mooney or Piper.


The assertion that the wing or tail section will break off is erroneous. Not necessarily. But you are operating outside the parameters of the aircraft and again, structural damage or failure can occur below Va.

If you challenge me, I would be willing to take up a Mooney and demonstrate that it is indeed possible to fly its wings off. Mind you, I'd want to do an emergency egress course and a parachute free fall course first. But then I'd just dive a Mooney to Vne (or beyond) and pull up sharply. (On second thoughts, never mind.)


Of course your'e saying this tongue in cheek, but as a skydiver and parachutist, and one who has experienced structural failure in flight in aircraft, I'll tell you it's a bad idea, anyway. I'd also like to add that exceeding Vne doesn't mean you're going to break up. A bigger issue is passing beyond a region of flutter testing for the airplane...and that's what should really be being discussed here regarding this accident...not maneuvering speed and not wing spar failures. Flutter.

The ailerons were separated. Not the wings. It wasn't the wings that broke up. It was the ailerons that separated from the airframe. Overloading a wingspar can break a wingspar, or break a wing. I have had an entire wing crack due to low level maneuvering (and a pre-existing unknown stress riser) at low level in mountainous terrain, in a large airplane...and at speeds well below cruise (no maneuvering speed for the airplane). Not in this case...something caused not the wing to break, but the ailerons to separate. What does that? Flutter.

Control flutter can occur suddenly. Its onset is rapid, and in a true flutter situation, violent. It can remove the control surfaces in less than a second, it it nearly always results in the loss of the aircraft. It can also predicate, or lead to an aircraft breakup.

I was only a few miles from the crash site of this aircraft when it happened. As I turned out, I knew nothing about it. The wind was calm, the weather fair, not particularly cloudy, no mountain obscuration. It's an uncontrolled area, little radar coverage (what you do have isn't useable for ATC purposes), nobody to talk to once you reach the elevation of the mountain tops. The entire area is very mountainous, with elevations ranging from 4,500' to 11,000'. When any wind is present, turbulence can be strong, ranging from moderate to severe or greater. On this particular day, there was very little wind.

Airplanes are built with minimal structure to save weight. Certainly one should remember that while limitations and numbers are given, airplanes can break at much smaller numbers, and care should always be taken flying the airpalne. I the case of this Arrow, we hae precious little information to go by. Guesswork does not become a professional attitude in the cockpit (which should be the hallmark of the private pilot, too); we don't speculate; we know. In this case, we don't know, and shouldn't speculate. Certain observations can be made regarding the facts, but there are far too facts upon which to base any reasonable assertions. For now, the best that can be said is this should serve as a reminder to operate the airplane well within the parameters given you, and not push your luck.

[IO540]

The G limit of the airplane isn't tied to Va

I thought the two were tied, by the fact that if you arrange for the wing to stall and thus unload, its design limit cannot be exceeded.

Flight at/below Va ensures that the wing will stall and unload before the design limit is reached.

That is why Va varies with weight. At lower weights, Vs is lower and therefore you have to fly slower to maintain the said margin. If it was not for the main spar stress, Va would not vary (much) with weight because the aircraft weight is carried primarily by the main spar. The elevator, in fact, tends to apply a downward force...

As you suggest, there are other ways to break things, without exceeding the main spar limits. But e.g. control (or other) surface flutter is not related to Va, it's related to Vne.

[modelman]

Sternone seems to have gone a little quiet

[Fuji Abound]

Sternone seems to have gone a little quiet

Quietly listening perhaps.

[Three Yellows]

Quote "What did you solo on by the way?"

Concorde, I shouldn't wonder....:hmm:



Surely it was one of the Wright Brother's early aeroplanes as we know that Sternone doesn't approve of training on Technically Advanced Aeroplanes.

[SNS3Guppy]

Flight at/below Va ensures that the wing will stall and unload before the design limit is reached.


No, it doesn't. Again, that's a myth that's sadly perpetuated by instructors today. The airplane can be broken well below Va.

Further, a stall does not ensure that the wing has unloaded, in fact, it can be stalled and in excess of its ultimate loading.

A stall does not automatically unload a wing, or control surface.
Va provides a margin under specific conditions with a specific rate of control deflection in which the greatest chance under those specific conditions exist that the surface will stall before becoming damaged. The structure can be pushed beyond it's capabilities long before that speed is achieved however. See my previous post.

The elevator, in fact, tends to apply a downward force...


Not in all aircraft, not in all conditions.

As you suggest, there are other ways to break things, without exceeding the main spar limits. But e.g. control (or other) surface flutter is not related to Va, it's related to Vne.


No. Flutter can occur at speeds well below Vne, and well below Va, too. Flutter is very much a control balance issue.

In the C-130, for example, we were restricted to 250 knots if anything at all had been done to the ailerons or other control surfaces, including painting a stripe. That restriction remained in effect until the control surfaces were removed, and rebalanced.

Steve Whitman, a prolific aircraft designer and homebuilder, died with his wife in a Whitman tailwind enroute to the Oshkosh airshow some years ago. The aircraft broke up as the result of aileron flutter due to a control imbalance when some pinking strips of fabric delaminated along the trailing edge. The ensuing flutter separated the ailerons and it cost him his life. His crime? Mixing two fabric processes (Stits and Ceconite, I believe). The incompatibility lost adhesion between the different fabrics and treatments, imbalancing the controls, causing flutter (well below Vne, mind you, and below Va), and abruply terminating the flight as the aileron separated from the airframe.

Normal flutter tests are done as dive tests above Vne; an airframe normally shouldn't flutter until those speeds. However numerous things can affect the flutter characteristics of an airfoil, including the control cable tension, pilot input on the control stick or yoke (including pulsing the controls by input, or stiffenign the controls by applying a death grip on the yoke), atmospheric conditions, air density, temperature, altitude, counter balances, stuctural stiffness, control stiffness, control geometry, etc. Flutter is dynamic instability, which can, once again, occur well below Vne. Or Va.

The G limit of the airplane isn't tied to Va
I thought the two were tied, by the fact that if you arrange for the wing to stall and thus unload, its design limit cannot be exceeded.


No. The G limits previous discussed involved certification limits, such as those applied to a given category of airplane (normal category limits, for example). These are not at all the same as design limit criteria, nor do they relate in any way to the ultimate airframe limits (the point at which the airframe will actually break).

Limits and flutter and even Va can become somewhat complicated subjects, as there's a lot more than stalling before the airplane breaks. Suffice it to say for now that one should understand that the airplane can indeed be broken at speeds less than Va.

Years ago I worked on a lot of single Cessnas. In particular the 200 series (206, 207, etc). I found numerous vertical stab attach brackets broken from slipping. Pilots don't often realize just how little is holding the parts of the airplane together, and many would be absolutely shocked to learn that some entire surfaces are attached with as few as two bolts. The single Cessna clan has the vertical stab supported with attach brackets, which came from the factory as aluminum brackets. These have mostly all been replaced with steel brackets (which sets up the subject of another separate discussion; dissimiliar metals corrosion, or electrolytic corrosion). The aluminum brackets were often found during inspections to have failed. Did this occur under high loads above Vne? Nope. Normal slips to landings as many instructors teach.
I used to throw big airplanes (large four engine airplanes) and small airplanes alike around in full slips, as my different employment required After enough experience in the shop I learned to stop doing that a long time ago. I've seen the results from simple, low speed slips. An enormous stress is placed on the airplane as a result of those sideloads. I've seen the same cracks and breaks on large airplanes during depot-level inspections when we've pulled the vertical stab as part of the inspection process. It can happen just as easily to the light airplane you own or rent locally, just from normal flying...and it's not something you'll be finding in the checklist or pilot operating handbook, either. Certainly something to keep in mind.

Your airplane most definitely can break at speeds less than the rough air, turbulent penetration, or maneuvering speeds. The presence of those speeds in your aircraft handbook doesn't mean you can't break the airplane below; it only means you should avoid abrupt control motions above those speeds. It means you can break them above those speeds, it doesn't mean you can't break them at a lesser velocity.

[Mark1234]

Seems I misread the initial post(s) to suggest that large control movements were the cause. However, it does state that 'outboard portions' of both wings had detatched, (as well as the ailerons).

I am curious however as to how a stalled wing can be producing more force than an unstalled, and exceeding the load limitations, through a reasonably feasible flight manouver up to and including Va?

At VERY high speed I can see it, but surely the whole definition of aerodynamic stall precludes there being more force stalled vs unstalled?

As for breaking it <Va - well, Va is for the full deflection of ONE control (usually pitch plane I believe), so if you start throwing in large deflections of other controls at the same time, that would seem reasonable.

[Pilot DAR]

Quote: :Hihi, Also i feel quit sorry for you that the only argument you can tell me is that i'm low houred not yet PPL rated.. comon, please do better than that, i could actually learn something from you guys.

Com'on Steronon,

You're really a super experienced, highly qualified pilot and maintainer, just stirring the pot for fun here right? I do find your posts really entertaining, in a laugh at the ridiculous kind of a way. If you really wanted to learn from those of us with a lot of experience, you'd ask intelligent questions, and not attach silly statements, with no basis of fact behind them.

The Arrow, as the other Piper aircraft of that lineage, are fine aircraft, quite deserving of their well established place in our industry, and longevity.

There was in past times, an AD against PA28 wings for structural inspection at the attachment. I helped pull a few for this inspection. Eventually the AD was withdrawn, because apparently (as we certainly learned) you generally did more damage getting to wings off for inspection, than the damage (none ever found by us) that you were supposed to look for.

Any aircraft can be broken if you abuse it (either deliberately, or accidentally) badly enough. Poor aircraft designs are uncompetitive, and just don't survive in our industry, much less prosper as well as the PA28 series.

Sternone, You're welcome to read more, and comment less. There is a whole lot of wisdom here, why not learn all you want, without annoying the contributors?

Pilot DAR

[SNS3Guppy]

I am curious however as to how a stalled wing can be producing more force than an unstalled, and exceeding the load limitations, through a reasonably feasible flight manouver up to and including Va?


A stall has nothing to do with unloading a wing. It has everything to do with exceeding the critical angle of attack for a wing or airfoil, to the point of airflow separation. This does not mean the wing is no longer loaded. The mere act of increasing it to that point may overstress the wing, stall or not.

A rapid pitch up for example may cause an accelerated stall, as could a turning stall with a load factor causing the stall to be higher than normal...as you understand, a stall may occur at any attitude and at any airspeed.

Rapidly causing a surface to stall, be it a wing or othewise, places a high load on one side of the surface and not on the other; the pressure distribution shows a rapid increase on the side against airflow. While the airplane may now be stalled, or may be rotating deeper into the stall, the load doesn't magically disappear, and may continue to increase, depending on the dynamics of the airplane. If you're doing local stall practice, straight ahead, poewr off, on a calm clear day, you may not perceive this...but you can certainly break an airplane in the process of stalling it...high speed or low. All one need do is exceed the ultimate load capabilities for any given component, and it need not be the spar.

One airplane I used to fly routinely lost 27,000 lbs during the flight in a matter of one and a half to four seconds, as part of it's mission assignment. It was a very stout airplane which underwent regular maitnenance and detailed inspections. I performed many of them myself. Four years ago on a normal drop, as the aircraft finished unloading, well below any design limits or maneuvering limits, the right wing folded back,the airplane rolled left and the left wing came off. Three seconds later it exploded as it struck the ground, killing three of my associates. A short time later, three weeks, another airplane I was regularly flying did the same thing. Both in undemanding conditions, both below design maneuvering speeds (no published for either one, but below the turbulence penetration speeds. The second crash killed two.

I previously identified American Airlines Flight 587 as having lost it's vertical stabilizer during a normal climbout, well below penetration speeds. It encountered some wake turbulence; the turbulence did not separate the flyin surface; the pilot did that with multiple control inputs. These inputs were within what was considered to be a safe flying speed, and were done in an aircraft which automatically determined how much was too much based on the airspeed and it's control logic. It theory, aerodynamically the airpalne couldn't break, and operationally it wasn't supposed to allow itself to be broken. But it was, killing a large number of people. Do some research.

Last year I did a brief assignment in a learjet. I had to attend a recurrent training in the type, and one of the things I noted was the addition to the Aircraft Flight Manual of statements regarding the ability to break the airplane at low speeds.

One should also remember that Va is predicated on a single event; one application of the controls in one direction under very specific conditions. In a typical turbulence encounter, we may move the controls both directions to counter a roll, yaw, or pitch excursion. Youv'e doubtless experienced this yourself...flying down final approach during a blustery, gusty day, for example. You may be very busy on the rudders and very busy on the control yoke as you fly...that's normal. However, Va doesn't account for anything but the first control input. After that, you're no longer on the charts, and this is something that's not taught...most pilots eroneously believe that so long as they're below maneuvering speed, they're okay. Not at all true.

At VERY high speed I can see it, but surely the whole definition of aerodynamic stall precludes there being more force stalled vs unstalled?


No the definition of a stall is exceeding the critical angle of attack for the flying surface...and again, has nothing to do with unloading the surface.

When I teach a student about basic aerodynamics, I like to ask the student if he or she has ever put his hand out the car window and "flown" it in the slipstream. Of course, everyone has. This then allows the student to understand much of what he or she needs to know, just from experiencing it with the hand. By slowly increasing angle of attack, the hand will experience an increase in lift, requiring less and less effort from the muscles in the arm to hold it up. At some point, past the maximum coefficient of lift when drag exceeds lift and we enter into a region where airflow separation over the hand increases, we see an enormous rise in induced drag and a drastic reduction in lift. The hand has stalled. Lift isn't there to hold the hand up, but now you have a lot of retarding force pulling the hand back toward the rear frame of the car window. Do it rapidly, of course, and you may strike your hand or arm on the window frame. The force hasn't suddenly quit; it's changed velocity (direction) and been given new vectors.

In a steep turn the airplane may be made to stall at a higher speed than one sees while straight and level. Pulling harder in the turn works up to a point when the angle of attack is exceeded, and the airplane stalls. But at that point, the wing has not unloaded. Rolling the wings level helps, if you're able, but pushing forward unloads the wings...even in the turn, and increases the ability to help roll out of the turn.

What we're not seeing in this mishap is a case of the wings being pulled off, but a separation at the outboard portions, with loss of the ailerons.

Again, do a little research on aileron flutter, which can occur at speeds considerably lower than Va, as well as high speeds. It's a complex subject, but flutter is very often a fatal event. The time from initial onset to loss of the control surface and loss of control is typically well under a second, and it's violent. Many things can cause it from a loose control to a control imbalance to air density to pilot input to excess speed and a combination of these things. Aircraft are flutter analyzed, and design tested and dive tested, but each aircraft is subject to it's own individual condition, and individual operating conditions. Since no detail is yet available regarding this particular mishap, that' about as far as we can reach and go with the topic...until more information is given.

As for breaking it <Va - well, Va is for the full deflection of ONE control (usually pitch plane I believe), so if you start throwing in large deflections of other controls at the same time, that would seem reasonable.


Mark, you raise a valid point there, except it's one control input...not just one control. That is, one movement to the left of the rudder, for example, or one movement right of the ailerons. Moving them back the other way, reversing the control input, changes everything, and may cause the airplane to break without any other inputs. Even below Va.

Your point is well taken that the use of other controls may put additional forces on the structure that take it outside it's design envelope. Rolling and pitching at the same time, for example, can put some severe uneven bending and twisting forces on the wing and on the fuselage, as well as on the control surfaces themselves. Some aircraft don't have a whole lot holding the control surface on in the first place...also something to consider. The structure is only ever as strong as it's weakest point, and that's seldom the control cable to which the pilot is roughly attached. Always keep that in mind.

[kiwi chick]

Oh my god! This is the most interesting thread I've read in my entire life I think! :ok:

I started reading it 'cos I fly a PA28... and was ready to quip that if doesn't break the way I fly it, it must be pretty sturdy ;)

But my goodness, SNS3Guppy I was riveted to my seat reading all that! And yes, it is all stuff I should know but I felt like I learnt a whole lot more! :)

Thank you! :D

(how did you LEARN all that?! I thought I was a PoF geek but now I feel quite humbled, hahahaha!! ;) )

[SNS3Guppy]

how did you LEARN all that?!


Unfortunately, the hard way.

[deice]

Interesting reading as always SNS3Guppy, but what you are saying is that normal flight can cause an aircraft to fall apart around us. We should all remain on the ground then! :eek:

Are you referring to the C130 that lost its wings unloading over a fire? There's a video of that on the web and it looks absolutely terrifying! But, aren't those aircraft subjected to abnormal conditions and flying in extreme environments, hot, low level and abrupt maneuvring? I always thought it looked exceptionally dangerous...

On another note, perhaps you've heard of the CASA 212 from the Swedish coastgaurd that lost a wing at low level flying just off the coast last summer. They grounded the fleet and I have yet to hear of any actual cause, but you have hinted on a few reasons. Very interesting indeed!

Keep up the lecturing please!

[IO540]

If Va is not related at all to the main spar structural limit, why does it vary with weight in the manner expected if it was?

I haven't been told this by an instructor; in fact I don't recall meeting an instructor who knew anything much "technical".

[Major Major]

Great post SN3G, very well explained.

Having just stepped out of a PA28 having done some steep turns and stall practice, I can happily report that it didn't fail.

Maybe my steep turns are getting better because the seat of my pants returned a reading of 2G. After reading this thread future readings maybe invalidated by me :mad: myself.

IO;
[Caveat - I'm a stude and you guys undoubtedly know more than me, I'm just suggesting a few ideas].
Could it be that for the majority of light aircraft surely Va is related to main spar strength in addition to other factors, if (as is detailed elsewhere) Va is usually determined by a single axis control input and it's usually the elevator.

I seem to remember reading that light aircraft were protected against spar failure because a rapid change in the lateral axis (i.e., elevator deflection) would cause the aircraft to stall before the loading on the wing became sufficient. However, having read SN3G's post and the AAIB report previously detailed in this thread, that looks like an exam question answer as opposed to the real world, where the forces on the aircraft (gusting wind, aileron changes).

However I think it's the AAIB report that points to a PA28 as having a spar that deforms at 5.7G - considerable.

[sternone]

Message to my fans over here: sorry i couldn't answer earlier, i was logging solo hours in the air this week, some of you insisted that i got more of that, well i'm doing my best, i'm happy to know that you guys all had your mouth shut until you got over 1k hours logged.

[gasax]

No sternone - just try to remember to think before blurting..

But if nothing else it started some interesting discussion.

Incidently the one inflight Mooney breakup (yes they do happen!!!) I found on the net, resulted (probably) from flutter.

But being unaware of the Bonanza's reputation is somewhat unforgiveable..

[Major Major]

Sterny baby
It's not how many hours you've got that counts, it's how you communicate your experience.

'No PA28s for me' probably isn't the best way of doing that.

This flutter thing is scaring the willies out of me but it seems to occur where there is some sort of related failure, e.g., the Whitman discussed below.

No chance of it just...happening... is there? I thought that modern aircraft had aerodynamic or mass balances to prevent it?

MM

[sternone]

In either case, this is a forum, so if you don't like me, i don't care, i don't have to live with you and you don't have to live with me. I learned so many things from PPRuNe it's amazing, and i like it. I'm only a click away from going away from your screen, how easy can that be ?

The one Mooney that broke up in flight was flying into a thunderstorm, the wing spar test they performed on the Mooney: the test rig broke before the wing spars did, they broke a static test fixture at 9,3G's while doing a destructive test on the J model.

Very intresting read about the flutter, be happy i say stupid things, we get these fine texts from it!!

http://www.mooneyland.com/mooneywingstrength2.gif

[SNS3Guppy]

Interesting reading as always SNS3Guppy, but what you are saying is that normal flight can cause an aircraft to fall apart around us.


Actually, I said no such thing.

Are you referring to the C130 that lost its wings unloading over a fire?


Among others, yes. I used to fly that airplane.

But, aren't those aircraft subjected to abnormal conditions and flying in extreme environments, hot, low level and abrupt maneuvring? I always thought it looked exceptionally dangerous...


The aircraft are subject to stresses above what most aircraft or operations experience; on an accumulated basis, various studies have concluded at a rate approximately 500 times aircraft in normal service. Dangerous, however, is a relative term; more a matter of perception. A phrase I used years ago, now on all our safety posters, is "It's not an emergency. It's our profession." Many people would be surprised to learn it's not like the movie "always," and is actually a technical, professional assignment.

Abrupt maneuvering is somewhat of a misnomer. In past times, however, aircraft over fires have experienced structural failures at speeds below turbulence penetration speeds (our drop speeds are considerably lower). The C-119, in particular, experienced a number of aileron and wing failures while maneuvering, even at low speeds, largely due to flitner tabs which allowed very light control forces and rapid pilot deflection of the controls. Abrupt movement suggests something different than a fast, but smooth application of the controls. The rate at which the airframe is loaded, as well as the amount and the way in which it is done, all combine to determine what's safe and what's not.

What we do, is make everything as normal as possible. An approach to a drop, be in the flats or on the mountainside, is flown like a traffic pattern with a downwind, base, and final, as stable as possible, configured similiarly to a landing (except for the landing gear, of course, and sometimes that gets used on a very steep drop). The point is, even in that type of flying, we strive very hard to keep airplanes way from the edges of the envelope, and to respect the airframe, and limitations.

This becomes extremely important when operating in severe or greater turbulence. Extreme care when operating the airplane and in maneuvering is very critial to one's own safety, and the longevity of the airframe.

[SkyHawk-N]

Oh yes Skyhawk-N, I made the schoolboy error of reading the whole thread and taking the quote by IO540 in context with the whole. I clearly forgot that there would be smart pedants reading waiting to seize on such a basic error.
You, on the other hand have managed to analyse IO540's post in splendid isolation and have skilfully proved him wrong as well as having a well justified pop at me.
Well done!

Why thanks cjboy, appreciate it. :ok:

Now getting back to your first post on this (what turned out to be) interesting thread.

All this wisdom from someone who went solo on 4th October 2007, and probably doesn't yet have a licence.

Why not cut sternone some slack? I may be wrong but english is his second language and as a result things may come out a bit wrong sometimes, this may be one of those cases. A friendly correction and steer would have been nice.

[hobbit1983]

My 2 cents; I once (unintentionally) dived a PA-28-160 to 2 knots past Vne. It was during IMC training, unusual attitude recovery. I was a little slow to recover during a diving UA (and I suppose so was the instructor!), and the ASI showed just past the redline.

A subsequent engineering inspection revealed no damage/stress/etc. We had plenty of height in hand, and recovered gently (it was a full power dive, but not at an overly steep dive attitude).

Undected faults aside (and also noting that I am not a qualifed airframe specialist/engineer/etc), I think had I, or the instructor, recovered with abrupt, substansial control inputs then there might have been damage to the aircraft or worse.

[PompeyPaul]

Why not cut sternone some slack? I may be wrong but english is his second language and as a result things may come out a bit wrong sometimes, this may be one of those cases. A friendly correction and steer would have been nice.Are you nuts ?!?!? That goes against the whole DNA of pprune. He said something that a few people disagreed with and must now be destroyed. Ideally, he should be hounded from the forum until he decides to never post again. Giving PPL students some slack, what a crazy idea...

[Final 3 Greens]

Yeah, get lost worthless studes :}

[deice]

SNS3Guppy, I know you didn't actually say that, but with all the parameters that can affect a break-up it sure sounded pretty close to it.:}

[deice]

Ok, I'm gonna stick my neck out again and prove I know nothing about this (after 15 years! :sad:).

I picked up my aircraft design textbook to try and understand where Va actually comes from. It says, "Maneuver speed, or pullup speed Vp, is the maximum speed at which the pilot can fully deflect the controls without damaging either the airframe or the controls themselves".
To me this suggests that at or below Va, movement of a control cannot generate the required aerodynamic load to cause a failure of any part of the airframe.
Further, Va is a speed picked as a design point and not actually defined from design parameters. It may be dictated by design requirements, or calculated through some empirical relationship.
Basically, the Va speed provides a point where the integrity of the airframe is checked. By analyzing the AoA or sideslip obtained by full movement of a control at Va, one can establish the airloads which the structure must meet. The text also implies that full movement of the ailerons at max load factor imposes instantaneous loads that frequently are critical to the wing structure. So pulling 3.8 gs and throwing the yoke could snap your wing, perhaps.

Sounds lika Va is a useful limit after all, but perhaps I'm not understanding what the book is saying. :sad:

[deice]

Thanks! Then I'm not completely in the dark after all. I need to pick up a few POHs and see what they say, but I don't recall ever reading anything about single axis movement, but I understand the point and it makes perfect sense really. I don't remember enough from PPL ground school to recall whether Va was discussed in this manner...

I shall be more watchful of my students as of now.:eek:

[tsenis]

Thanks for your contributions

[Pilot DAR]

Quote: be happy i say stupid things, we get these fine texts from it!!

It'd be even better if you were to say smart things, we could then have fine texts with no nonsense in the middle of them.

Yes, I probably said a few silly things when I had less than 1k hours. In the 4k hours which have followed that (some in Mooneys), I've learned to be respectful of others, and simply try to behave well, as if I were I were in the same room with all of you...

Pilot DAR

[Pilot DAR]

Those wiser than I ware welcomed to comment, but my read of FAR Part 23.335 Design Airspeeds, (c) Design Maneuvering Speed Va, refers only to a formula relating to stall speed and the limit maneuvering load factor (G's). No other axis are mentioned.

It is therefore my understanding that Va is considered in isolation of the other two axis, and control inputs in those axis.

There is, therefore, no design assurance that a pilot will not damage the aircraft with full and abrupt use of ailerons or rudder during flight at speeds below Va.

That said, aside from perhaps aerobatic flying, how common is it to need to apply such control inputs in any axis anywhere near Va? In all my years of flying, I've only needed to hit a control stop twice, Once crosswind landing (okay I'll step into the fray: Ailerons in an Arrow), the other the elevator down stop, which I held for some time, to maintain control during a test flight of a horribly misrigged Cessna 206. Both of these events were very close to stall speed, thus breaking the airplane with control input was not a concern. Breaking it against the ground was though!

Pilot DAR

[IFMU]

Can I ask again if anyone has a link to the NTSB report that started this thread, I'm hopeless at searching the NTSB web site, I'm interested to know if the ailerons fell off because the outer wing sections failed or whether the ailerons came off first

G-EMMA,

Here it is:

http://www.ntsb.gov/ntsb/brief.asp?ev_id=20071105X01726&key=1

It doesn't really say what happened first. It just said the ailerons were found detached. The UK accident report seemed to indicate that the aileron was seperated on G-BKCB because the wing failed between the two piano hinges. So, for a moment, the aileron was all that was holding the wingtip on.

I have followed the story, and the thread (minus the personal bashing), with some interest as I'm working on my instrument rating in an Arrow. She's an old girl, 1967 PA28R-180, with something like 4000 hours on it. I sure would like to know exactly what happened in both accidents, that I might learn from it.

Personally I have a lot of faith in the PA28 series aircraft. They have been around a long time. And I agree that any airplane, no matter how strong, can be broken if overstressed. Here's my favorite:

http://www.ntsb.gov/ntsb/brief2.asp?ev_id=20001208X08467&ntsbno=MIA97LA211&akey=1

There was a longer story about it in Soaring magazine, I should have kept it. This old timer flew into a towering cumulus cloud, became disoriented, and pulled a wing off a 1-26. Spun out of the bottom of the cloud. The pine trees stopped the rotation, then cushioned the fall. The glider ended up on its nose. His injury consisted of a cut shin stepping out of the cockpit. His wife took to calling him "Heaven's reject."

A couple years ago I met a structures guy from the company. We talked about that accident. The guy had to pull 9 g's to fail that wing. There's no way I could pull 9 g's in a 1-26 in any normal part of the flight envelope. He had to be going fast, as well as yanking the controls.

-- IFMU

[sternone]

In the POH of the C152 it says at flight load factor limits:


Flight load factors:
* Flaps Up: +4,4g, -1,76g
* Flaps Down: +3,5g

* The design load factors are 150% of the above, and in all cases, the structure meets or exceeds design loads.


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

[Major Major]

Are those G limits instantaneous or sustained ? The POH probably won't say.

Could you comment G-EMMA in terms of testing? I'd imagine they'd put components into a test rig and subject them to testing until deformed, therefore it would be sustained.

I would imagine that in one or two of my more creative landings, I've subjected the airframe to a significant amount of G, though without an accelerometer even my finely tuned seat of pants wouldn't be able to say how much.

Also in turbulence or gusty conditions you can get bumped around significantly - again, without some sort of instrument I can only guess as to airframe stress.

I too fly old PA28s - about 1976 I think, with 1000s of hours on the airframe, probably mainly by low hours or ab initio PPLs, so they've probably been submitted to a bit of everything.

[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]

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 (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/sharedcontent/dws/dn/latestnews/stories/111607dnmet3deadplane.2bb9edf.html

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

A couple of pictures of the plane involved:

http://www.skymates.com/fleet/images/large/N55307-05-072.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! :uhoh:

[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]

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]

:D 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! :E)

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]

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 ?

[Radar]

Sleeve Wing,

My thoughts exactly, when I came across this thread a couple of days ago. It has been "time for the Mods" for some time in relation to this ' gentleman', IMHO.

[DX Wombat]

I shall be saving this thread for my own future reference. :ok:
There is one thing which hasn't been mentioned so far regarding break-up in flight and that is unreported, and therefore unchecked, bumps to the aircraft. (I am NOT saying that this is implicated in this case.) This report on G-DELS (http://www.aaib.dft.gov.uk/publications/bulletins/december_1996/pierre_500558.cfm) makes chilling reading. The pilot knew he had hit something, did a very cursory check then set off again with fatal results. All the more reason for having those seemingly minor bumps checked out by an engineer.
Sternone, as others have said, your attitude to people who really DO know more than you is worrying. None of us is perfect, but if I make a mistake, and I have made many, I acknowledge the fact and try to build on what I have been told is the correct version of matters. As one of my former FIs said (of another student) "I foresee a starring role in an AAIB report for him." You really DO need to think, listen and read carefully. I don't want to hear that you have become another statistic.

[sternone]

Anyways, i will try to be more gentle and not go into replys and atacks on my comments. Maybe it's a rolling stone and i have no problem at all taking the responsibility on me.

I will see what future will give and will see how other users of this forum will do, in my opinion i still think users should be allowed to give their consern on a certain insident but as i understood it seems to be better to keep personal comments for me own, just like in real life ?

I hope some of you accept this, we'll just see how it goes. If you take this as an appoligy of some of my comments to you if i have hurt you, please do so!

[VFE]

I fear Sternone is yet another one of those PPRuNe personalities whose main intention is to stimulate user debate centred largely around themselves or their assumed online persona rather than anything of substance and relevance to the raison d'etre of this oft abused website.

Do you feel ignored in your real life Sternone? That is probably because you have nothing much to bring to the table. Hence my advice that you perhaps ought to listen instead of rabbiting for once - then maybe when the weight of your knowledge equals the weight of the chip on your shoulder you too might bring something to a (ridiculous) debate. However, as you rightly state, it is indeed your choice, and I'm not really fussed moreover I just feel for those at your chosen training establishment who appear to be tasked with a job beyond the call of duty, namely that of winding your neck in sufficiently enough for you to learn something about flying.

But until then you'll be pleased to know that this here cherished thread on PPRuNe is all yours so please have a good sunday on me whilst I sleep content in the knowledge that I'm not tasked with the apparently thankless job of sitting next to you on your flying lessons. :)

VFE.

[IFMU]

I am very interested to learn more about the failure mode of the last 2 PA28R's. In the UK report on G-BKCB, they mentioned no evidence of fatigue, corrosion, or anything else wrong. Are the UK investigators blessed with scanning electron microscopes, etc for looking at this stuff? Is the FAA? I just hope the right technical people do the analysis so we can come away smarter.

-- IFMU

[SNS3Guppy]

There is one thing which hasn't been mentioned so far regarding break-up in flight and that is unreported, and therefore unchecked, bumps to the aircraft. (I am NOT saying that this is implicated in this case.) This report on G-DELS makes chilling reading. The pilot knew he had hit something, did a very cursory check then set off again with fatal results. All the more reason for having those seemingly minor bumps checked out by an engineer.


This is an excellent point, especially with respect to rental aircraft. We really have no way of knowing what the last student, the last instructor, the last renter did to the airplane. Did he overstress it? Did he run the engine too lean, cause detonation, and set the engine up to fail on my flight? Did he "shock cool" something, overstress something, tweak or twist something for which the airplane will mete out vengence on me?

Metal remembers. Fatigue is cumulative (which is why it's called fatigue). Cracks grown, damaged areas are weakened...and mechanical things do not repair themselves. Problems don't go away. They just hide for a while.

I believe I mentioned previously the C-130 that shed it's wings. I was in the airplane about five years prior to it losing the wings, when a pilot decided to show is anger at being kept out in the field months longer than he desired. He made a combat landing (short field, roughly speaking) so hard that it pulle the map case free from the cockpit wall, and it hurt. I mean hurt. My neck and back. He was the pilot flying, and I had no idea he was going to do what he did. I have a personal suspicion that he intended to break the airplane in order to go home.

I personally removed the wings on that airplane as part of a team doing inspections on two small cracks discovered. The cracks weren't discovered then, but while out of the country on an assignment. When we entered the wing structre to do ultrasonic testing, the two small cracks we'd discovered visually and identified with dye penetrant inspection were found to be inisible, but extnding the full circumference of the wing. If you don't know the early model C-130 wing, it doesn't have anything holding it together but thick skin. Internally there are hat-section stringers and some shear web spars that don't really carry a load so much as for the fore and aft walls to the integral fuel cells...crack the skin on the wing, the wing is coming off. The crack went all the way around both wings. Only a very small bit of it was actually visible.

We immediately removed the wings, stripped them, replaced one, repaired the other, and began instituting inspections involving stripping wing sections and performing dye penetrant and ultrasonic inspections every week or so. Even with that elevated inspection schedule, the wings still came off some years later.

Past sins can be paid today, but you may the one paying even though you didn't commit the crime. Yet another good reason to carefully respect the limitations of the airplane and not stray too close to the edges.

In another thread on this forum just lately a discussion has been in play regarding ultimate load bearing capability on the airplane...it's published for these numbers XXX, but it can really stand a hundred fifty percent of these numbers...so we're okay, right? Wrong. The airplane has been stressed and bent and twisted...so we're not gauranteed anything Metal remembers. All those other stresses to which that airplane has been subjected? They're still there, waiting for more. Like a big spinning prize wheel, but big question is when will it stop, and who will be the lucky winner when it does?

Some years ago drop studies were done to explore the reasons that perfectly intact cherokee airframes have been found with dead occupants. The airframe is in good shape from outward appearances, but the occupants are all dead of crushing injuries. Why? Drop tests from different heights and different angles with high speed photography showed that the airframe deformed substantially on impact, crushing the occupants and killing them, then springing back to look relatively intact and normal.

Is this a weakness in the design? No, not really. The airframe of an airplane is a very flimsy, weak structure; it's designed with minimum strength, and it's chief citeria is that it's aerodynamic, and it's light. Unlike fabric airplanes of old, the Cherokee is not built around a reinforced stress-frame steel cage. It's just bits of 6061 and 2024 aluminum riveted together. Add speed and gravity...don't expect it to perform miracles.

It's a strong, well designed airplane. The gear system design, particularly with automatic ram-air sensed gear safety and other such features, is ridiculous. However, it is what it is. The pitch is particularly sensitive, being a flying tail, and the potential to overcontrol the airplane does exist. What this calls for isn't fear, but common sense. Many production copies are out there flying safely...jump in one and you can too. Push the airplane beyond it's limits, and that privilege is no longer yours...just as you've been taught since day one a student.

The biggest weakness in any airplane is the pilot.

[IFMU]

IFMU, The AAIB report for G-BKCB looks robust enough, they didn't find fatigue, corrosion, or anything pre-existing as in my opinion it wasn't there to find. The finite element model they created is convincing,...
Metal remembers. Fatigue is cumulative (which is why it's called fatigue). Cracks grown, damaged areas are weakened...and mechanical things do not repair themselves. Problems don't go away. They just hide for a while.
I spent a part of my aerospace career in test. We would chug on metal parts until they busted, then send them out to the metlab. The metab would put the parts under a microscope, look at grain stucture, origins, etc. Under the microscope you could see what parts were ripped apart by fatigue, and then as the part got weaker static overload would take over and finish the job up quickly, assuming the initial fatigue damage was not detected with non-destructive test. We would take all the test data and figure out s-n curves, to help in predicting the life of parts. Miner's law, cumulative damage and all that.

What struck me about the G-BKCB report was the one liner:
Also, no evidence was found in the failed area of the wing of corrosion, fatigue cracking, repairs, material defects, or any other feature, which could have degraded the strength of the structure.
Maybe the investigator turned the pieces over to the metlab, they did the detailed analysis, electron microscope study, etc of the failed parts and the terse one liner came out of the results of that report. Or maybe not. Why would they do a detailed analysis of the metal, and not show it, then do a detailed FEM analysis, and present it in gory detail?

I have seen a lot of FE analysis. It's a great tool. But it is not always right. I've seen it both ways, where somebody comes along and does a FE analysis of a 30 year old part with a million fleet hours on it and says it only has a 5 hour life. I've also seen parts that were shown to have huge margin in analysis end up with a limited life and a redesign. Even if the FE model for G-BKCB was spot-on, it seems all that it did was to validate the static strength of the PA28R spar splice area. I bet that part was designed, static tested, and shown to have margin over the standard category g-loads a long time ago.

-- IFMU

[Contacttower]

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



The comment was meant to be half in jest...hence the ;). To be fair though the Spitfire tended to be subjected to much greater in-flight loads than your average GA hack. Part of my point as well was the assertion by Sternone that the Bonanza was strong- it is, but as someone reminded us earlier in the thread the early ones did have a very well know reputation for loss of control in flight and subsquent break up.

[sternone]

Part of my point as well was the assertion by Sternone that the Bonanza was strong- it is, but as someone reminded us earlier in the thread the early ones did have a very well know reputation for loss of control in flight and subsquent break up

Sure, the 33 model was just a downgraded model of the V-tail, but without the V-tail .. at that time people valued the V-tail higher than any other tail.. might worth noticing that there are no in flight break ups of the 33 model...

[hobbit1983]

Sternone - sorry you're wrong, see here, page 39 -

www.caa.co.uk/docs/33/CAP701.pdf

This document lists a Beech Bonanza 33 which broke up in midair over France, following loss of control in IMC.

[IO540]

Wasn't the V-tail Bonanza back end modified at some stage, which put a stop to the breakups?

There is a big technical advantage in a V-tail: instead of three huge things dragging in the airflow, you have just two. No wonder the new SE jets are V-tails (Cirrus and Eclipse, IIRC). It's got to be worth 10-20kt, which at the relevant cruise TAS is worth an awful lot of fuel flow.

I bet you will notice when the yaw damper servo packs up though ;)

[Tony Hirst]

Some interesting thoughts on a couple of Beech T-34s suffering in flight break ups too.

http://www.avweb.com/news/pelican/182086-1.html

You many need to register.

[hobbit1983]

IO540; link to a piece on the history of the V-tail.

http://www.tsgc.utexas.edu/archive/general/ethics/vtail.html

Tony; interesting article, thanks.

[scooter boy]

"Wasn't the V-tail Bonanza back end modified at some stage, which put a stop to the breakups?"

Yup - twas a simple fix, they just stopped selling them to doctors!:p
i:e If you had an MD you needed the conventional tailed model!
Death rate plummeted!
SB

[IO540]

Thank you for the V-tail URL, Hobbit. Fascinating.

Quote from it:

Out of the over 10,000 aircraft made, less than 250 were involved in fatal in-flight accidents.

That is one helluva lot of deaths.

[wsmempson]

2.5% OF V-Tailed bonanza's involved in fatal accidents? Wow. Is that right? 250 out of 10,000 would suggest that it is....:eek:

[SkyHawk-N]

That's why, in the States, Bonanzas have the nickname "Doctor Killers", or "Fork Tailed Doctor Killers".

[Tony Hirst]

Great link Hobbit.

I can't help but notice this quote in relation to my thoughts on Post #8 :hmm:
The in-flight break-up rates of most single engine airplanes with retractable landing gear were significantly higher than for other categories of general aviation aircraft.

[IO540]

The in-flight break-up rates of most single engine airplanes with retractable landing gear were significantly higher than for other categories of general aviation aircraft
Sure, but because they are more slippery (and thus a pilot not paying attention will end up exceeding Vne sooner), not because they have retractable gear.

The availability of reasonably slippery fixed gear GA planes capable of ~ 150kt+ is a recent thing. It was done as a marketing stunt in the USA, where the insurance companies are throwing their weight around more than here. In reality it was just a stunt and hasn't worked because the premium on say a Cirrus SR22 is most definitely not lower than on say a TB20/21. But if you have a relatively inexperienced pilot then the "simplicity" of fixed gear is a rewarding yarn for the salesman to spin.

Fixed gear is itself a compromise. To make it low drag you have to have tight wheel cowlings, which compromises grass field / general dirt runway capability. Even the much looser PA28 cowlings are routinely dumped to avoid these problems - look at any flying school fleet.

[IFMU]

My dad used to fly a Debonair back in the early 70's. He told me there was a rash of wing failures due to people flying into convective weather. The accident pilots hit an updraft of 1000's of feet per minute, and tried to hold altitude with pitch. Like any glider pilot could tell you, the airspeed builds if you try to hold alitude in lift. Then you hit the downdraft on the other side, and suddenly want to go down at 1000's of feet per minute. Haul back on the yoke, at high airspeed, pull the wings off. That was the speculation of the day as to what was happening to the doctors. Not all a fault of the v-tail. My dad flew myself and my two siblings through some bad convection while skirting a thunderstorm. He asked for, and received a block of altitude rather than a single altitude. The recommendation of the day was to hold the attitude, and airspeed in bad convection and let the altitude go up and down if it was safe to do so. I barely remember it, I was 4 at the time. It made a big impression on my 13 year old brother, who vowed to never get into an airplane with my dad again. It also scared the hell out of my sister, but she was into horses and not airplanes.

The T-34's that shed their wings have the same structure as the bonanza/debonair. Fatigue rears its ugly head. Usually fatigue is the domain of the helicopter, due to the many load cycles its parts see. But run the loads up, it takes less cycles.

-- IFMU

[Mark1234]

There is a big technical advantage in a V-tail: instead of three huge things dragging in the airflow, you have just two. No wonder the new SE jets are V-tails (Cirrus and Eclipse, IIRC). It's got to be worth 10-20kt, which at the relevant cruise TAS is worth an awful lot of fuel flow.


Not necessarily so cut and dried.. if you have a V tail the 2 bits are (generally) larger than the equivalent 3 bit versions - it's all swings and roundabouts.

V's were very en-vouge for gliders for a while before they worked out there wasn't that much advantage over a more traditional tail - glider types are very fastidious about aerodynamic efficiency!

[Tony Hirst]

IO,

With regards to recent aircraft, rather than the 70's design context of this thread. I simply don't know. The dangly bits have to add drag but then the top TASs are for the 'faster' turbo normalised ones are quoted at 25,000' where air density is about 50% less. Not sure if this is relevant to the types we've been discussing thus far.

[sternone]

Sternone - sorry you're wrong, see here, page 39 -

www.caa.co.uk/docs/33/CAP701.pdf

This document lists a Beech Bonanza 33 which broke up in midair over France, following loss of control in IMC.

indeed, i see it, aldo i don't see what exact 33 it is, i had info that the F33A did not had any breakups...

[wsmempson]

I think that the truth here is that PA28's are close on the most common GA type in the air today. If grossly mishandled they can break - as indeed will any other aircraft. Therefore there will be a greater body of anecdotal evidence of accidents involving PA28's than most other aircraft, simply by dint of the numbers flying.

Compound that with the reality that, because the bulk of the pa28's are basic, non-complex, machines operated by salt-of-the-earth basic PPL holders - accidents will happen.

Contrast this scenario with complex aircraft such as mooneys, beechcraft, tb20's (or indeed the more complex iterations of the piper family) where pilots have more hours, more training and have survived their early hours post ppl, and now have gained an appreciation of what constitutes sensible handling and what constitutes MISHANDLING and the figures change.

A book called "The Killing Zone" paints this picture far more elloquently than I but suffice to say that I believe that we all stand a far greater risk of dying as a result of one of our own errors (cfit, fuel mis-management, showing off at low level over one's neighbours house, etc) than as a result of our Piper Arrow falling to pieces in the air.

Training and experience are paramount in our field and more likely to save our lives than grounding the PA28 fleet for spurious reasons.

I would finally like to point out that 34.7% of statistics are simply made up on the spot...:rolleyes:

[Major Major]

Almost WS; it's 81.6%.

[Cf Vic Reeves on some advert or another].

Edited to ask whether the Killing Zone is a jolly fine book and worth purchasing?

[sternone]

Edited to ask whether the Killing Zone is a jolly fine book and worth purchasing?

It's not bad for a read, but it's not the top... is it worth purchasing, no, is it worth reading, yes.

[wsmempson]

The Killing Zone is a pretty interesting read. The main thrust of which is two-fold;

Firstly there is a statistical 'spike' post PPL of accidents experienced by pilots with between 100 and 350 hrs under their belt. The theory espoused being that the pilots in this 'zone' had enough confidence to fly in challenging conditions, but not enough experience to do so successfully (or enough experience to know not to leave the ground at all).

Secondly the take-up of instrument training has a hugely positive effect on the numbers of accidents arising from flights into IMC or CFIT and this has been aided by a more attainable qualification.

One of the examples quoted was the JFK II accident, which seemed to combine both of the writers points.

However, rather like Panorama these days, you could probably condense the message into a much slimmer tome, but it's still a worthwhile read, Quite why we can't translate the second message (which seems perfectly clear) into an attainable, JAA-wide, qualification in something approaching a reasonable timeframe is beyond me....

[sternone]

I remember reading it that he is against touch and goes .. i found that rather weird...

[sternone]

Yes, but G-EMMA, do you imagine learning landings while doing each time full stop landings ?? I did so far over 200 circuits...

[Contacttower]

I remember reading it that he is against touch and goes .. i found that rather weird...


This came up in the OBA crash thread....and I kind of find it a little stupid as well; many flying schools in the US will not allow solo touch and goes even when operating from 1000m+ of tarmac because the risk of loss of control is too great. Most people in this country would find a rule like that a little strange...but to be honest I can see that touch and goes are more 'dangerous' than full stop landings.


It's not bad for a read, but it's not the top... is it worth purchasing, no, is it worth reading, yes.


Just out of interest sternone what books on GA safety would you recommend actually buying then? Considering that that we must all admit that GA does not share the excellent safety record of the airlines.

[hobbit1983]

Stats aside, I found the book a very good & interesting read.

WS; I agree, I did my IMC before I started my hourbuilding and am very grateful for doing so. If it was fully JAR etc it would be even better.

[sternone]

Just out of interest sternone what books on GA safety would you recommend actually buying then?

Well i bought it the killing zone because i wan't to support aviation writers as much as possible and i just buy a lot of books, and yes, to your suprise maybe i actually read them, i hate watching tv.

I find 'be a better pilot' by alan bramson much better... also i find that reading 'stick and rudder' made me a safer pilot..

what books do you advise ?

[Contacttower]

what books do you advise ?


I have to admit that I haven't read many GA specific flying books other than those needed for the PPL/Night/IMC courses. As far as other aviation books are concerned....

Spitfire: The Biography is quite good and so are many of the Battle of Britain classics like First Light for example.

Handling the Big Jets gives a very interesting insight into how big planes fly (if you're into that sort of thing which I slightly doubt many in this forum are)

The Compleat Taildragger is probably the best book written on taildraggers for the novice conventional gear pilot.

[hobbit1983]

"Fate Is The Hunter" by Ernest K. Gann :ok:

Getting back on topic.... I don't think touch & goes are as safe as full-stop landings either, but I still do them periodically to brush up my skills, especially on taildraggers.

Spinning/stalls aren't as safe as straight & level flight either, but they've still got to be done to maintain skill currency.

Sternone; I was curious about how many Bonanza 33s were involved in breakups in midair (I agree btw; the later models and Beech in general, do seem to have the reputation of very well built aircraft from what I've read) and a look on the NTSB website, searching for Bonanza 33s, revealed that (during the first few pages anyway) that most of the fatal accidents seemed to involve CFIT/loss of control during IMC.

[Mark1234]

Yeah, I'm against touch'n'goes too. (In my vast, just got my PPL experience :) )

You combine (probably) the two most dangerous bits of flight (t/o and landing) into a short space of time, with the requirement to re-configure the aeroplane in between while you're eating up tarmac at maybe 40odd kts (throw in say 3-5sec for the electric flaps to wind in)

You arrive at the ground with a mindset of leaving again. Possibly you're pressured to get it down because you're worried about space, or possibly you just have the mechanical process at the forefront. Either way you don't really have an accurate handle on where you're going to be off the ground by - I can make a visual estimate of where I'm going to depart the ground from a standing start (in typical conditions), I have little idea where I'm going to on a touch and go, certainly at my experience level.

You can find with the workload up, maybe at a strange aerodrome, you do something inexplicably stupid, miss toggling the flap switch and become airborne with 40deg of flap like I did. (Fortunately it was well managed, the instructor was with me, and we didn't park it in the trees at the far end).

Not to say they shouldn't be done in the right circumstances, but there are plenty of reasons why they are dangerous, and not a good idea.

[Contacttower]

The touch and goes thing is perhaps getting slightly off the point of the thread....but this is what I think:

On the PA28 when doing touch and goes before my PPL I was advised to not use the third stage of flap so that when I touched down I didn't have to bring it up again for take off. This worked fine.

On short fields you've got to have good judgement regarding how far down the runway you're going to let the plane float before hitting the TOGA button and trying again and also recognising when to stop and taxing back for take off rather than attempting to take off again from the roll. That needs to be emphasised during training

When I started on the Super Cub the touch and go became perhaps slightly more hazardous...my instructor told me to raise the flaps and wind the trimmer back before taking off again (all this while rolling down the runway) which on more than one occasion lead to me almost loosing directional control....one day I tried just leaving everything and taking off with full flap...and actually that was a much better idea...the Cub will lift off in about 100m and I swear I've taken off before with the ASI reading zero! (It is a very old ASI).

On the C152 I find the flaps a little fiddly to get to the right notch...but if you don't need take off flaps (when one tarmac) getting them up is easy.

The last OBA crash was arguably party caused by a loss of control doing an (unauthorised) touch and go.

I think they are safe and will continue to do them though.

[hobbit1983]

Contacttower, agree with you on the Supercub - I've done the same, but far more impressive for me was the reduction in power when I forgot to put the carb heat back in :O

Was once doing a touch and go in the 152TT, and managed to retract ALL flap from full flap, rather than the incremental stages I'd wanted, due to hamfistedness. That was interesting too!

[Slopey]

In answer to Sternone's question about 200 landings - I did mine at OBA and each time did full stop, back to the hold - it only added a minute or two on to each one - I was still managing 7/8 circuits and hour, which is more than enough when you're learning!

They do teach t&g's but not when solo. Wasn't a problem really - did plenty of em with the FI on board, and a threw it away plenty times too when starting out.

Anyway - apologies for the thread drift ;)

[Contacttower]

Was once doing a touch and go in the 152TT, and managed to retract ALL flap from full flap, rather than the incremental stages I'd wanted, due to hamfistedness. That was interesting too!

We obviously fly at the same airfield!- I have to say G-DRAG can be a bit of a pain doing touch and goes....it can be quite reluctant to lift its tail sometimes and it doesn't have the performance of the Super Cub.

I have done exactly the same thing with the flap before (once in the air!:ugh: :=) but luckily the flap retraction mechanism on the C152 is quite slow!

[Contacttower]

I did mine at OBA and each time did full stop, back to the hold - it only added a minute or two on to each one - I was still managing 7/8 circuits and hour, which is more than enough when you're learning!



Thing is though I've sat in a queue of more than four aircraft at Ormond Beach...and while I wasn't doing any touch and goes there I always thought that that rule was possibly a bit frustrating and expensive!

[hobbit1983]

I do prefer the Supercub for tailwheel flying (especially if it's had it's new radio fitted!) however warming to G-DRAG recently. Managed to get it in and out of Chilbolton with 2 up earlier this year (one of which was an instructor I might add!)

Glad it happened in the air to you (rather than anywhere else) - as you say it is slow, I thought I'd selected one stage retraction during the latter half of the touch and go, but as my workload was high/capacity full etc etc I didn't notice I'd accidentally dropped the lot off until the lift just kept on dropping off too!

Anyway, back to thread, any aircraft will most likely breakup if mishandled/put through suffcient turbulence, Bonanzas are built stronger but not immune, and I will still fly OSFC's Arrow despite the fact that one disintegrated recently cos I love it to pieces :ok:
(sorry for the flippancy, rather long day, still in the office slaving away!)

[deice]

Contacttower - clearly that ASI needs replacing. If it's very old then the speed has run out and can't be refilled again...

On a different note. The discussion about touch'n'goes or not is interesting. I did plenty of them when doing my PPLs way back (I feel ancient but it was only 15 years ago). Now that I'm an instructor and see things from a different perspective I've come to appreciate that as an instructor you need to be very cool (as in relaxed, not Rayban cool) if you're going to let a student do TnGs on first solo, or subsequent solos.

As someone pointed out, some of the risks involved with TnG include the focus shift required from landing and then taking off. I've noticed with a few of my recent students that they can't keep the centerline in the vicinity of the aircraft when rolling for the take off, while a stop and go makes things completely normal. If I'd let them go alone I'd have to pick them out of the woods. The other issue I find is in the stressed situation after settling. Because airspeed is much higher than normal in the beginning of a take off, the aircraft is close to flying speed and some students end up wheelbarrowing down the runway before I can persuade them to get the stick back. It's not a perfect situation, but I think eventually most students manage TnGs rather well and it does maintain a certain flow in the pattern.

[IFMU]

I did about 100 hours before I did a T&G according to my logbook. Learned to fly in a PA12. I don't think I've ever done a T&G in a super cub or a pawnee, but those are working airplanes. I have done them in the cessna 140, though I find it is easier to leave the flaps either all the way up or just 1-2 notches.
-- IFMU