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 Post subject: King Air Wing Strap
PostPosted: Sat Apr 29, 2006 12:59 pm 
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What is the theory behind this and if it is such a good addition why do they not come out of the factory this way?

Also........the Beech 100 wing has 4 attach bolts to hold the outer wing to the main section. If one bolt fails in flight will the other 3 share the load and give the pilot a fighting chance to get back on the ground or is it game over?



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PostPosted: Sun Apr 30, 2006 12:38 am 
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The wings came off some of the Beech one being a TC calibrator and even though Beech never admited to a design fault a strap was designed and I guess its an option.

Cant say Ive ever heard of one bolt failing and you might have to ask Beech Engineering for an answer.



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PostPosted: Sun Apr 30, 2006 11:30 am 
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I, and a former chief pilot I worked with, did a bit of a study on the Saunders Strap and the Beech wing bridge.
Keep in mind I am a pilot, not a mechanic. The whole problem started when an old Beech 18 shed it's wing. Old Beech 18's never die, they just become night freighters. A further check found a series of cracks in the "bathtub" fittings where the bolts that hold the wing on to the center section cracked. The "bathtub" fittings are aluminum blocks attached to the spar caps and the wing. The center has a hollowed out pocket to allow the insertion of the big special bolts and washers (expensive). To solve the problem and remove the 500 hr xray requirement, Saunders developed a spar strap that was a fail safe device that would carry the air loads in case of a failure. Since the Beech King Air has the same system, the problem followed. First was a King Air 90 out of California that shed a wing. Corrosion on the bolts that hold the wing on was the main culprit so Beechcraft came up with a 6 months mainenance schedule to solve the problem. TC had a Beech 100 that shed a wing. Investgation discovered the 6 month manditory inspection had been passed over for many years, plus the airplane was subjected to a high stress environment of a lot of high speed, rapid turning pull up, low level flights as an airways check airplane. With the Beech 200, as far as I was able to determine, corporate aviation in Canada was responsible for most of the press on the spar strap. It was one way corportate pilot could protect thier jobs because very few chater King Air's had the strap becauseit was not manditory. It simply reduces the number of inspections required. Beechcraft claimed the the airplane was perfectly safe without the spar strap IF THE INSPECTIONS WRE DONE. To compete with Saunders, Beech developed an external wing bridge that solved a problem that did not exist. While all this shit was going on, Beech lost a lawsuit where a Bonanza engine caught fire in a 1966 Bonanza and the argument was that since Beech saw fit to change the engine, (Continental IO-470 to IO-520), in 1967, the 1966 model was defective. Cost Beech about $78 million. So Beech were reluctant to introduce a change to fix a problem, as opposed to increasing performance. Finally, with the Beech B200 Super King Air, an internal bridge, called a Super Spar, was eveloped and the problem has gone away. This is why the Alberta Government requires a 18986 or newer King Air for their Air Ambulance. The consultant they hired was involved with charter aviation and was familiar with the whole mess. A lot of the discussion was brought on by Saunders, who had a vested interest in the whole thing. If memory serve me correctly, 85% of the Saunders Strap installations were to Canadian registered airplnes. Finally, as ledgend has it, an Austrailian Beech 200 witout the strap was subjected to a severe overstress when the crew became incapacitated by loss of pressurization. When the crew regained thier facilties, they overstress the airplane beyond design limits and the outer wing panels failed, but the bathtub fittings survived, proving that the design was solid, that lack of mainenance was the problem. A senior TC official, (name slips me) was asked about the King Air series airplanes and he said that if there was ever any doubt about the safety of the King Air series airplane, TC would do something about it. Ledgend has ir that the union reprsenting TC pilots wanted the Spar Strap but the mechanics wanted the Super Spar internal bridge so to apease everyone, they did both. Because TC put a strap on the airplanes, all corporate airplanes had to have one. To give you an idea of the corporate culture in Alberta during the hey day of the oil patch, we were to do a trip in our Beech 200 for a customer who operated both a King Air 100 and a 200. When we pulled up to the hangar, a person there said he did not know whether he should allow his executives ride on this airplane because it was not equipped with brake heat or high flotation tires. It was warm spring and we were going from pavement to pavement. Find out later this was the hangar attendant, the one tasked with the job of sweeping the floors and cleaning the windows. The aviation dept. was shut down a few months later. Too expensive.
Just remember that most of this material is for the most part, unsubstanciated and the notes were with the chief pilot who has since passed away. But I am sure if you investigate, you will find most of what I say is true.


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PostPosted: Sun Apr 30, 2006 3:24 pm 
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Thanks a bunch OLDTIMER for a real decent response to my question. Now to go one step further..............the newer Beech 350's and 1900D's...........the same 4 bolt system or has the overall design been changed?


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PostPosted: Sun Apr 30, 2006 6:41 pm 
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Same 4 bolt per wing basic design but many improvements, usually called the Super Spar. What maintenance requirements there are I am not sure but IF IT WAS A WEAK POINT IN THE AIRPANE, THERE WOULD BE RESTRICTIONS. I am not at all familiar with the 1900 other than they share many systems and there are no flight restrictions that could be related to a weakness in the design.
Beech appears to have gotten around some of the product liability by
A.) The General Aviation Revitalization Act that President Clinton signed into law which limits the liability manufacturers have to carry. All Beech 90's, 100's and early 200's were certified to a different standard than the new ones. I believe the old 99 has the same wing design as a 90 or 100 and there are a whole bunch of those suckers flying around with a jillion hours on them. The manufacturer now carries liability for 19 years. After that, you are on your own.
B.) The Beech 300, 350, 1900C and D are all "new" designs certified to a different category than some of the older airplanes that were the subject of the lawsuits.
At least in my humble opinion.
It was a fasinating study trying to explain why a charter company could fly an airplane without all the expensive mods the private corporate airplanes required. As far as the corporate pilots were concerned, it was empire building. Finally, CEO's started to ask why they could charter a King Air, complete with crews and fuel and all the expenses plus a profit for the air carrier cheaper than their bare bones cost of ownership. As a result, with a slowdown in the energy business (well before 9-11) most corporate flight departments were shut down and the companies chartered where required and the wing strap contoversy died.


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PostPosted: Mon May 01, 2006 3:35 am 
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Good post Oldtimer, I remember chatting with you about that, at one of our former YVR company's. The only thing I will add is that the new Wing "super spar" is different in mainly the LWR FWD bath tub attach. They did away with the Tub idea and turned the bolt into shear not tension and into a fork style fitting. In fact this is a mod for older bath tubed A/C too but I think only TC did it on there older 90"s.


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PostPosted: Mon May 01, 2006 8:23 am 
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The 300 350 are old school designs with the outboard wings bolted on. The 1900 series has a one piece wing, tip to tip no "wing break" no bolts.
The 1900 "C" and "D" model have different certification from each other and the smaller Kingair series but,... I don't think thats why their construction details differ.



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PostPosted: Mon May 01, 2006 4:39 pm 
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actually the 350 and 1900 are both one piece wings not sure about the 300 though


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PostPosted: Tue May 02, 2006 7:12 am 
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I think I can add some info to this beyond the "political" aspects. Keep in mind this is what was told to me at a B200 course, so 100% accuracy???

Under the head of these bolts is a small radius and accompanying these bolts are champfered washers. I have heard that the plane that really got the spar straps started was the TC plane and that it had the washer put on backwards as only one side was champfered, easy mistake to make if you're not paying attention! On a wheel, you might get away with one like that, but on the lower forward wing bolt, it won't. I'm not sure the time frame involved, but sooner or later the stress causes the bolt to fracture under the head, and in a high-G manuver, the other three won't hold the wing on. SO! According to Beech, if the aircraft is maintained in accordance with the maintenance manuals, then you would install the washer on the nut in the proper manner, and install the bolt and torque it to spec, and you will never have a problem. However (and this is second hand) to avoid costly lawsuits, Beech subsidizes the wingbolts to make them cheap so that if there ever is any question to them, or you install one wrong, realize it and pull it back out, you can just replace it. They don't want to take any more chances, their name is at stake. Another thing I am not sure about is that the washer under the head of the bolt is champfered on both sides now to make it idiot proof. My plane is sent south for the heavy maintenance and I've never seen it out yet. I'm thinking as I write this as well, that the later versions of the plane, the lower forward bolt was changed from a tension fitting to a shear fitting, once again not 100% on that one. The bathtub fittings have some pretty low tolerances on damage limitations for corrosion and gouges/scratches, etc. as well.

One of our planes has the Saunders strap and another has the Beech strap. Others don't have any. The beech one definitely looks like a complete afterthought, just slapped on the bottom of the wing. You'd think it'd lose a few knots by how it sticks out the bottom. The Saunders is a lot more fair and low profile, but I suppose if you need it at all, you probably don't care how it looks.

Cheers! :)



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PostPosted: Tue May 02, 2006 11:52 am 
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Understanding the Beech/Raytheon King Air Wing Attach System


There is a lot of mis-information floating around in regards to the reasoning behind the application of the fail safe strap system - The Saunders Strap and the Beech Bridge. Hopefully this will help rather than confuse.

History

Beech had a very successful aircraft in the B17 Staggerwing design. This was a metal tube aircraft with a fabric covering and is considered to be one of the most graceful aircraft of its’ era. The Beech 18/C45 series of aircraft was developed by the company using mostly all metal - fuselage and wing construction. However Beech decided that the center section of the aircraft wing spar was to be of a metal tube construction - this could be for engineering reasons or simply because they could use the existing talent pool of tube welders. If this is removed from the aircraft it looks just like a miniature bridge truss (Warren Truss). When installed into the fuselage it provides the hard points for the landing gear attachment and for the outer wing panel attachment.

The Beech 18 was developed and produced during WWII and shortly after - most of the aircraft were delivered to the military. One of the serious drawbacks to using tube structures is internal corrosion. One of the most common methods used to combat this was to use an corrosion preventative (LionOil) that was injected into the structure through small holes that were then plugged. This was labor and time intensive and since the expected life of this aircraft was calculated in years rather than decades this step was omitted on many military aircraft. These aircraft found there way into the civilian market and formed the backbone of many smaller companies around the world.

Then the aircraft suffered from wing failures - the cause being traced to internal corrosion in the center section metal tubing. A stringent inspection process was put in place that included an x-ray component at specified time intervals. Sometimes this program was not enough - in my early days in the early 1970s’, one of our competitors’ aircraft suffered this fate - the float aircraft left with a load of cement, couldn’t get into where it was going due to weather, and returned to base. On approach a Piper Cub on floats initiated a take-off run and the Beech on final initiated a go-around with a right turn. The wing separated and the aircraft crashed. Both engines were buried 14 feet into the ground. The aircraft had just returned from having the wing x-rayed but the x-rays had not yet been developed. You can imagine the rest of the story when they did look at them.

A small Canadian company - Saunders - designed a fail safe strap system for the Beech 18. This consisted of a metal strap that went form wing tip to wing tip along the underside of the wing. The theory here is “Redundant Load Path”. In other words if the original structure of the wing should fail, the external strap would take up the load and prevent catastrophic failure. Installation of the strap took some engineering and when removed or installed 1000 lbs of ballast had to be placed on the wings to pre-load them. Once installed the ballast was removed and the strap was already pre-tensioned and when flying would share the load. The best fix would have been to remove the wing spars and replace them with new spars that were corrosion proofed - but this was a very costly option. Unless the spar actually showed signs from the inspection program of defects - the operators were very reluctant to spend any more than they had to on these old aircraft. Many operators attached the strap as a way of using the aircraft in a safe manner until the corrosion got bad enough that the aircraft needed a new center section spar. At that point they parked the aircraft. The Saunders Strap was a very successful piece of engineering and allowed these aircraft to operate for an extended time safely.

The King Air Wing “Problem”

When we trace the ancestors of the King Air we need to go right back to the Twin Bonanza and the Queen Air. These were post war aircraft and build on newer technology and the metal tube frame center section was gone - replaced with an aluminum web construction. Beech still retained the center section and outer wing panel construction method because it makes sense for both production and maintenance. The attachments used to attach the wing to the center section were accomplished by the use of bolts in tension and were situated in the “Bath-Tub” fittings. These recessed fittings were not a Beech invention - many other aircraft like the Douglas DC6 used this technology so the method was a proven design.

One of the issues that Beech had to contend with was where the bolts were located - not as big a concern in the Queen Air as it had piston engines - but when the first King Airs’ were produced with the PT6 engine - the front mounted exhaust stacks produced a soot trail that included some of the wing attachments. Now Beech had to contend with a bit more of a corrosive environment. Since the aircraft were operated all over the world under a variety of conditions corrosion became a major consideration and Beech solved the problem with an inspection program and a calendar time on the attach bolts. It would be the inspection program that would cause most of the headaches with this aircraft. Removal and inspection of the wing attach fittings is detailed in the Structural Repair Manual (SRM) and involves taking one bolt out at a time - inspecting the attach fitting using NDT methods, inspecting or replacing the bolts as required and the correct torqueing of the fasteners after.

During this process it is possible for several things to take place. The first one is MID - Maintenance Induced Damage - this is when the attach fitting is damaged by a maintenance procedure - the damage tolerance allowable on the Bathtub fittings is carefully controlled by Beech. Any damage found must be reported to their engineering department and they will evaluate and provide a repair/replacement process. It is easy to do and they have seen just about every condition that you could imagine. Any corrosion, cracking, coining, scratches etc. must be reported as per the structural repair manual.

The second issues comes with the fastener “Stackup”. This is how the washers etc. are placed on the bolts and is critical to the integrity of the join. To add to the confusion different models and differing serial numbers within models have different bolt part numbers and washer stackups - it is very critical to know you have the correct parts to install. It is through the stackup process that the Transport King Air shed its’ wing.

The bolts used in tension on the King Air wing system are high strength and have a small radius from the head to the bolt shank. This is normal engineering for high strength in tension as the radius prevents the stress from concentrating in a sharp corner which will reduce not only the ultimate strength of the bolt but also the fatigue life. To ensure no damage occurs, a washer with a chamfer is used - the cutaway part of the washer will not contact the small radius on the bolt head. In the case of the Transport King Air, the washer was put on backwards - the sharp edge of the washer was contacting the radius and formed a concentric stress riser around the head of the bolt. Even though the bolt was correctly torqued, the degradation of the ultimate strength was sufficient to cause the bolt to fail.

The importance of the bolts cannot be over estimated - Beech states that “The Loss of Any One Bolt in The Wing Attach System Will Cause Catastrophic Failure” In other words there is no redundant load path - and for the certification requirements for this aircraft - none is needed. Beech/Raytheon maintains that there has not been a single case of structural wing failure on a King Air aircraft that was not the result of maintenance issues or operational overload. The system as designed is safe when properly maintained and if the aircraft is flown within the flight envelope parameters. Beech couldn’t / wouldn’t admit to a design flaw - most likely because of legal ramifications and lawsuits.

When the wing came off of the Transport aircraft there was a lot of concern in the industry as to the safety of the aircraft design and a lot of armchair pundits put in their 2 cents worth. As a result the aircraft gained a reputation (most undeserved). Since the Saunders Strap was so successful with the Beech 18 wing problem, the company quickly offered it as a method of ensuring the safety of the King Air as well. There was a lot of political disturbances in regards to the aircraft, and owners, operators, and passengers became wary of flying in the aircraft - just as had happened with the Beech 18. Many companies put on the strap as a way of placating their passengers and crews. The reality is that after the hullabaloo wore off and saner minds prevailed, the aircraft was cleared and the focus was switched to maintenance procedures. The strap was a knee jerk reaction - but has remained an option as it does provide a fail safe load path - just in case something happens.

Beech/Raytheon has gone the extra mile on this issue with education and due to possibility of bolt failures from bogus parts they have provided a lowest possible cost for the attach bolts. They have tried to make it as inexpensive as possible for the operator to get genuine parts from the manufacturer and prevent bogus substandard parts being used.


The Beech Bridge

Loyal Beech owners and operators did not like the idea of having to modify their aircraft with the non-Beech Saunders strap system. They wanted to know why Beech didn’t offer an alternative - thus the Beech Bridge was born.

Beech had 2 options on the spar strap issue - the first was to buy the Saunders strap - they decided it was going to cost too much and opted for the second option which was to produce a spar strap themselves. The problem was that Saunders had a patent for the strap and Beech could not just duplicate it without legal implications. So the engineers designed a strap that was “different”. The difference was that while the Saunders strap was a flat plate from wing tip to wing tip, the Beech bridge was shorter - after all the wing tips weren’t falling off and the strap was placed on spar blocks - so the strap was not flush like the Saunders strap. If you have the Beech bridge you can tell by the fairings under the wing that cover it up. This was sufficiently changed from the Saunders strap that patent infringement was not an issue. Both the Saunders strap (Now Avia) and the Beech bridge provide a redundant load path.

The King Air Grows Up

Operators are always wanting the gross weight of an aircraft to be higher so they can make more money with the aircraft. The very successful Super King Air 200 was pushing the small aircraft weight limitations. Beech was very aware of the legal implications that would occur if they changed the design on the production line to a different style of wing attachments. They knew that a fork attachment with a bolt is shear for the lower forward bolt - this is the one that has the highest load as the lift and drag forces are greatest here - would provide a solution and increased confidence in the aircraft. B200 s/n BB1434 and BB1444 were used by the FAA to approve the over 12,500 lb gross weight of the aircraft. This upgrade in weight class gave Beech the necessary reason to introduce the “Super Spar” or as they refer to it “The 3 Element Spar”.

From that point on the new spar was used on the aircraft. It is a good system and can be retrofitted ($$$$) on earlier aircraft if wanted. These aircraft have no need for the spar strap kits as the strength of the join is incredible. Thus the heavy B200 and 300 series aircraft have an upgraded spar. By the way - there is no official B350 - it is still classified on the type certificate as a B300 - it just has wing tips added. The 350 designation was just the way Beech differentiated it form the straight wing 300.

I think - but could be wrong that the Beech 1300 - used as an interim aircraft between the 200 and the 1900 has the same wing system as the 300 - the Beech/Raytheon 1900 is designed to a completely different type specification and the wing structure is different.


I hope this clears up any confusion you might haveover the King Air wing attachment issues.


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PostPosted: Tue May 02, 2006 5:56 pm 
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The B300 was certificated to SFAR 41, this had a sunset clause in it. The 350 came after certified to FAR 23 and has a one piece wing, with winglets, uprated -60 and stretched fuselage. here is the pertinent ADRegulatory Information

91-12-10 BEECH: Amendment 39-7021. Docket No. 90-CE-57-AD.

Applicability: Models B200, B200C, and B200T airplanes (serial numbers (S/N) BB-1158, S/N BB-1167, S/N BB-1193 through BB-1203, S/N BB-1207 through BB-1312, S/N BB-1314 through BB- 1334, S/N BL-124 through BL-132, and S/N BT-33), and Models 300 and 300LW airplanes (S/N FA-2 through FA-190), certificated in any category.

Compliance: Required as indicated, unless already accomplished.

To prevent in-service fatigue failures and to allow continued operation of the interim safe life limit of 15,000 hours TIS for the lower forward wing attach fittings, accomplish the following:

(a) For Model 300LW airplanes, upon the accumulation of 8,300 hours TIS or within the next 100 hours TIS after the effective date of this AD, whichever occurs later, modify the wing spar attachment by installing Beech Kit No. 101-4050.

(b) For Model 300 airplanes, upon the accumulation of 9,000 hours TIS or within the next 100 hours TIS after the effective date of this AD, whichever occurs later, modify the wing spar attachment by installing Beech Kit No. 101-4050.

Further the B350 piggybacks it's type certificate on the 300(350) but TC groups it for ratings at least so far I'll follow up with the FAA



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PostPosted: Wed May 03, 2006 7:35 pm 
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Anyone interested in the wing spars on the King Air aircraft should end up very well informed by all the contributions on this post.

The King Air series and the 1900 aircraft Have FAA Type Certificate a24ce and this is available by downloading off the FAA site. Due to the small aircraft / big aircraft weight line Transport Canada has put them in 2 different categories for operation in Canada.


I have the following information from the Web, The structural Repair Manual (SRM), from the FAA Type Certificate, plus information on the Beech Modification Kit 101-4050.


From the Web:

219 King Air 300s were built when production ended in 1991.

Production of the 300LW ceased in 1994 after 35 had been built. The LW is a Light Weight version that was primarily produced to get away from high landing fees in Europe.

Over 220 King Air 350s delivered.


From FAA Type Certificate a24ce:

VIII - Model B300, Super King Air 350 (Commuter Category), Approved December 12, 1989

Model B300C, Super King Air 350C (Commuter Category), Approved September 7, 1990

For Notes, refer to Data Pertinent to Model B300 and B300C


NOTE 3. Mandatory retirement times for all structural components are contained in the FAA Approved Limitation Section, Chapter 4 of the Beechcraft B300 Maintenance Manual. (For FL-1 and up and FM-1 and up) and

Chapter 4 of the Beechcraft B300 Maintenance Manual Supplement 130-590031-67 (for FN-1 and up).
These limitations may not be changed without FAA Engineering approval.

From the King Air (SRM) Structural Repair Manual:

Wing Inspection procedure for B300 aircraft:

B300 Fl - 1 and after
B300 FM - 1 and after


Chart Item #201 and figure #201 show the lower forward shear bolt installation.

Chart Item #210 - No bolt inspection - this is due to the requirement that the bolt must be replaced with new after removal regardless of time in service.


From the AD:

Beechcraft 300 Series Aeroplanes

AD/BEECH 300/2 Wing Fatigue Life Limitation

Applicability: All models.
Requirement: For aircraft serial number FA-2 to FA-190 inclusive:

(a) Modify the lower forward wing spar attachment fittings by installing Beech Kit No. 101-4050, and

(b) Retire from service the wing centre and outer section main spar lower cap assemblies, including the attachment fittings.

Note: FAA AD 91-12-10 and Section 4-00-00 of the Beech 300 Service Maintenance Manual refers.

Compliance:
For Requirement paragraph (a):

For Model 300 LW aeroplanes, prior to exceeding 8300 hours component time in service; and for Model 300 aeroplanes, prior to exceeding 9000 hours component time in service.

For Requirement paragraph (b):

Before exceeding 15 000 hours component time in service.


This AD requires the installation of cold-expanded bushes into the wing attachment lugs, to improve their fatigue characteristics. The unmodified lugs failed well short of the interim 15 000 hour life when fatigue tested. Beech is conducting further tests on the modified lugs with a view to extending the fatigue life beyond 15 000 hours. This requirement is based upon a Country-of-Origin FAA Airworthiness Directive and fatigue tests carried out by the manufacturer.


I have never seen a one piece wing assembly on a Beech 350 - BUT I have not seen every one of them either!!!!!!

- if someone has pictures and/or documentation from the manuals I would love to see it.


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PostPosted: Thu May 04, 2006 4:40 pm 
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When I google searched "kingair 350 wing bolt" I found an ad that reflected a 1991 350 that had wing bolt replacement and wing bolt inspections accomplished. I guess at least some 350's are bolt on wings.


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PostPosted: Fri May 05, 2006 7:07 pm 
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Only seen 2 of them, and I purposely looked for the little covers over the bolts, I'll try to get a picture, but I'll have to get one of you to post it


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 Post subject: Re: King Air Wing Strap
PostPosted: Sat Jun 09, 2012 8:41 pm 
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Hello,

Does anyone know the price to acquire and install the Saunders Spar strap on a C90?

Excellent thread BTW.



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 Post subject: Re: King Air Wing Strap
PostPosted: Sun Jun 10, 2012 9:02 am 
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Probably outdated info, but there is an Aviadesign listed in whitepages as:

Aviadesign 375 Durley Ave Camarillo,CA 93010 Ph (805) 484-4681



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 Post subject: Re: King Air Wing Strap
PostPosted: Sun Jun 10, 2012 3:15 pm 
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Hi

Just to clarify, all King Air 350's have bolt on wings.. Not the one piece type like the 1900.

I have worked on them as a mechanic since 1990.



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PostPosted: Sun Jun 10, 2012 3:27 pm 
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rigpiggy wrote:
The B300 was certificated to SFAR 41, this had a sunset clause in it. The 350 came after certified to FAR 23 and has a one piece wing, with winglets, uprated -60 and stretched fuselage. here is the pertinent ADRegulatory Information

91-12-10 BEECH: Amendment 39-7021. Docket No. 90-CE-57-AD.

Applicability: Models B200, B200C, and B200T airplanes (serial numbers (S/N) BB-1158, S/N BB-1167, S/N BB-1193 through BB-1203, S/N BB-1207 through BB-1312, S/N BB-1314 through BB- 1334, S/N BL-124 through BL-132, and S/N BT-33), and Models 300 and 300LW airplanes (S/N FA-2 through FA-190), certificated in any category.

Compliance: Required as indicated, unless already accomplished.

To prevent in-service fatigue failures and to allow continued operation of the interim safe life limit of 15,000 hours TIS for the lower forward wing attach fittings, accomplish the following:

(a) For Model 300LW airplanes, upon the accumulation of 8,300 hours TIS or within the next 100 hours TIS after the effective date of this AD, whichever occurs later, modify the wing spar attachment by installing Beech Kit No. 101-4050.

(b) For Model 300 airplanes, upon the accumulation of 9,000 hours TIS or within the next 100 hours TIS after the effective date of this AD, whichever occurs later, modify the wing spar attachment by installing Beech Kit No. 101-4050.

Further the B350 piggybacks it's type certificate on the 300(350) but TC groups it for ratings at least so far I'll follow up with the FAA


The "350" is actually a B300, the 350 tag is just a marketing name. The serial number prefix for the B300 is FL. The BB prefix is for the 200, the old straight 300 is prefixed FA.

This AD is not applicable to the 350 (B300).



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