Ask the Expert: Answers to a Variety of Good Questions from Readers

Ask the Expert: Answers to a Variety of Good Questions from Readers

Q&AartI always appreciate when readers of our magazine take the time to contact Kim Blonigen, our editor, with operational questions they would like me to address. I try to reply as rapidly as possible to the person who is posing the question. Sometimes, ideas for an entire article or two are prompted by the question(s), whereas at other times a brief personal response is all that is necessary.

This month I will present the questions and my answers to a variety of topics that have been received in 2015. To all who wrote to us, thank you for your input!

The first question comes from Ray Orr, Chief Pilot for Air Charter Coordinators of Brisbane, Australia. Ray wrote, “In the King Air magazine, the photo in a Raisbeck advertisement of the belly of a King Air 200 while in flight shows that a wing strap has been fitted. Could Tom explain the strap history? We don’t see many straps here in Australia and the industry experts are mostly too young to know the real history.”

Oh boy! Now here’s a meaty topic upon which I could spend a lot of ink! I will give a rather abbreviated version of the story here and suggest a Google® search for those who want to read even more about wing spar straps.

David Saunders of Camarillo, California, president and owner of Aviadesign, came out with a Spar Strap for the Twin Beech 18 after there had been seven wing separations and the FAA mandated a strap modification, yet Beech offered no strap kit. A few years later, in 1974 and 1975, two relatively low-time model 99s (19-passenger, unpressurized, PT6-powered, commuter planes) showed up with lower main spar problems and Allegheny Airlines commissioned Saunders to develop a failsafe strap for the 99 that would extend the wing spar life past the low 10,000-hour life that Beech had mandated in response to the problems’ appearance. Beech’s fix was to come up with the “Super Spar” in which the bolt’s bathtub fittings were integral with the lower spar cap. (This design was also used on the first 1,000-plus 200s, as well as on F90s.) To change from the old to the new spar was a huge job that only a few Beechcraft facilities could accomplish, and it was very expensive with a lot of downtime. But Mr. Saunders’ strap provided a “secondary load path” by connecting the left and right outboard wing sections to each other via a strap that ran through the wheel wells and under the fuselage. The outboard wings were modified with two doublers – one running almost to the tip, and a second one terminating near the tie-down ring. The strap was bolted to the doubler just outboard of the wheel well. Before the holes were drilled and the strap bolted on, 1,000 pounds of sand bags were placed on each wing tip to flex the wings down so that the strap would always be carrying some of the lifting loads.

There was concern about “galvanic corrosion” between the steel strap and the aluminum wing and spar structure, and the spar cap was insulated from the strap in the wheel well.

Beech, of course, thought that Mr. Saunders was Satan himself, succumbing to the NIH (Not Invented Here) syndrome and cutting a great deal into their sales of super spars. The strap did not eliminate the requirement for bolt and bathtub fitting inspections and one drawback was that the strap needed to be removed for that inspection. Later, Saunders made a revised strap that was widened around the bolt location and had a hole in the center that allowed inspection while still installed.

Some of those 99s that should have been parted out when they hit 10,000 hours are still going strong with the strap with over 50,000 hours. Saunders went on to develop and sell straps for almost all King Air models. In the late 1970s, two King Airs – one was an E90 and the other a 200 – had the lower forward wing bolt break in flight. The 200 (after the crew heard a “snap” and observed the outboard wing making small movements on its own!) landed successfully, while the E90 had the wing come off, crashed and killed the one occupant. In both cases, tests showed that the bolt had been weakened by “stress corrosion.” It was a real fiasco of a time as all bolts had to be pulled and inspected, and more problems were being caused when this was done incorrectly, especially when a washer was installed backwards, gouging the fitting. The outcome was (1) putting the bolts in a lubricated environment instead of “dry,” (2) instituting an inspection and replacement requirement for the bolts, and (3) offering a nickel-alloy “Inconel” bolt that was much more corrosion resistant and allowed longer inspection/replacement intervals. (I doubt that any steel bolts remain in King Airs.)

Saunders jumped into the fray with a very extensive advertising campaign that implied the King Air wing was unsafe without that secondary load path his strap provided. Many, King Airs had the strap added. A Canadian Government flight inspection King Air lost a wing, too. (The strap is very popular in Canada!) Personally, I think it is unnecessary – with proper bolts and inspections – but I have nothing against an airplane with a strap. In fact, unless someone points it out, most pilots wouldn’t even notice it.

I was actually in attendance at a King Air Maintenance and Operation Symposium held at an NBAA convention in the early 1980s. Linden Blue was then the relatively new president of Beech Aircraft. He was sitting in the back of the crowded room and observing a rather contentious exchange between the Beech customer support people and the somewhat angry operators who were needing assurance that the wing was safe. Mr. Blue stood up, was recognized from the podium, and asked for a show of hands of all of those who would feel more comfortable if there was a secondary load path. Well over half of the hands went up. Then Mr. Blue said something to the effect of, “Well, if so many of you want it, then we’ll provide it for you, using Beechcraft quality design and manufacturing.” You should have seen the look of surprise and horror on the faces of the Beech customer support and engineering people there! After telling people why the strap wasn’t necessary and what a waste it was, their boss had just “endorsed” it and put them on the hook to make one!

So off to the drafting boards they went and came out with the “Beechcraft Center Section Bridge”… they couldn’t call it an evil “strap,” after all. Because of the argument they’d made about the dissimilar metal corrosion concerns, their strap was made of aluminum. Hence, it is about three times as thick as the Aviadesign strap, has a huge fairing that sticks down quite far below the fuselage, and is ugly as sin. To “hurt” Saunders, they charged the same price as his – about $50K, I think – and lost at least that much on every kit.

In a few years, the furor had died down, Beech had come out with the totally new lower forward wing attach fitting for King Airs, in which the bolt goes through “knuckles” and is now under shear, not tension, load, and the “need” for any type of strap faded away.

The second question comes from pilot Chris Donnelly. He writes, “When parking the airplane after a flight, I always move the prop levers back into the full forward position after shutdown has been fully completed, before I put the control locks into place.

I have been doing this for about 20 years now and have never found a reason not to. It’s just my personal way of leaving the aircraft until I return for the next flight. Most guys are taught to leave the prop levers in feather until the next flight, but my reasoning was that you have to push them forward before you initiate the start anyway, so why not return them to that position once you have completed a normal engine shut down? I have never noticed any difference in the start in any way, whether they were moved forward just before start, or whether they were left that way overnight.

This is something I have wondered about, but no one has ever been able to explain exactly why the POH recommends leaving the levers in feather after shutdown is complete.”

There is absolutely no reason that your habit is bad in any way, Chris. It is my guess that the checklist is written as it is so that a pilot in a rush to exit the cockpit and get to the cabin door to aid the passengers’ egress does not place the prop levers back forward too soon, before the props have stopped, which could lead them to start partially unfeathering again. But so long as they have truly stopped – or darn close to it – then there is no downside. I, too, often do it your way, just getting one step ahead of the game for the next start. (Although there are times I start in feather, to reduce noise and prop wash.)

In fact, I see one tiny advantage of your procedure: As you may recall, the prop governor has a spring that is always trying to push the speed select lever to maximum RPM, so if the cable connection ever comes loose, the governor will go to and maintain maximum speed. So you are placing that spring in its natural, relaxed state, rather than leaving it stretched to its limit. Take that, naysayers!

Matthew Robinson wrote, “I have a question for Tom regarding the electric landing gear systems in King Airs versus the hydraulic systems that replaced them around 1984 and after. Are the electric systems more failure prone, or at least more maintenance sensitive with frequent replacement of motors, switches, wires, and retraction chain for the front gear?”

No, I don’t think there is a significant reliability difference between the electromechanical and electrohydraulic landing gear systems. The hydraulics are a bit easier to rig without limit switches to adjust, yet shops are very familiar with the old system since it has been around for so long (beginning with the Twin Bonanza). There is a very slight advantage in the newer system since it has a totally separate emergency extension line going to each actuator yet failures of the normal or the emergency system in the older as well as the newer styles are very rare.

I think other considerations – engine times, avionics, modifications and appearance – would play a larger role in my decision making when buying a used King Air than the type of gear it has.

Lew Marden had this query: “I am currently flying a B200, BB-1896. Is it acceptable to have fuel transfer from the main tanks into the aux tank? We are experiencing a transfer rate of between six and 12 gallons per 24-hour period while the plane sits on a level floor inside a hangar. Also, is it common for King Airs to have inaccurate fuel gauges?”

Hello Lew,

Where are you located? The biggest enemy of accurate fuel quantity gauges is moisture. Here in the American Southwest where I live, the gauges usually remain quite trouble-free, once the access panels to the quantity probes and the wiring coming out of the probes have both been carefully sealed to prevent the ingress of new water. However, it is not uncommon for the gauges to be inaccurate for a while after a wash job, until things dry out. Those operators who are based in moist, humid climates fight a lot more problems in this area and it is sad, but true, that the gauge accuracy is not generally a King Air strong point. I surely wish the 200s, like the 300s, had an independent low-fuel-warning system – an optical sensor in the nacelle tank – but they do not, not even as an option.

As for the fuel migrating from the mains back into the aux – no, that should not happen. There are three vent connections at the top of the nacelle tank – under that oval plate – and if one or more of them leaks, it allows the backwards flow to take place. (There is also a return path back through the jet pump, but seepage here is not as common as from the nacelle top.) This is most likely to happen when the plane lands while still transferring aux fuel, before the auxes are empty, if one follows the Beech procedure precisely. I recently wrote an article for this magazine about the problems associated with “over-stuffing” the mains with aux fuel, and this takes place all the time unless you use our “trick.” The trick is to keep the left and right Aux Transfer circuit breakers pulled as standard practice, only pushing them in at Top-of-Climb, when you have aux fuel, then pulling them again when the auxes go empty. This eliminates the pressurizing of the mains and goes a long way towards alleviating the type of situation you are observing.

The final question comes from Aircraft Maintenance Manager Fixed Wing Fleet, Carolinas HealthCare System /MedCenter Air, Ken Blevins, who writes, “The first question is: In the King Air B200, if the brake de-ice is left on, the landing gear is retracted after the 10-minute time delay that turns off the brake de-ice system, does the “Brake De-ice” annunciator remain illuminated or does that annunciator turn off? We have looked at the wiring diagrams for this system and we do not see a clear cut circuit that would turn the “Brake De-ice” annunciator off if the system is turned off by the time delay printed circuit card.

The second question: In the King Air B200, what prevents the propellers from going into the Beta range or even into Reverse if the power levers are selected to the Ground Fine or Reverse positions in flight?

Apparently our pilots are being told by CAE / SimuFlite that it is ‘not possible’ for the propellers to enter Beta range or Reverse in flight even if someone was brave enough (stupid enough?) to try it.

I have been working on all series of King Air aircraft for over 20 years now, and I do not believe that there is anything installed on the King Air airframe or on the PT6 engines that would actually prevent or make it impossible for the propellers to enter Beta or Reverse in flight.”

Hi Ken,

First, yes, the Brake Deice an-nunciator should extinguish if the timer times out. Go ahead and try it on a flight or two; it won’t hurt anything, especially if you turn it on at altitude where it’s cold. Did you read my recent article on this system? A couple of comments from there: First, even if the gear is up for only a few minutes – say, three – and then the switch is turned off, the timer keeps running,
so after the total 10 minutes elapse, it won’t be able to be activated for the “rest” of the time. Second, it can be reactivated by, of course, extending the gear, but also by cycling the circuit breaker.

As for the second question, it looks like CAE/SimuFlite is putting out some bad information. We can only enter Beta and Reverse when the propellers are in an underspeed condition, turning at less than the selected propeller governing speed. Depending on the exact model of propeller installed, even with the propeller governor set at its maximum speed (2,000 RPM) and with the power levers at Idle, the indicated airspeed must still get below 110 knots or so before the propellers will finally encounter their Low Pitch Stop and hence start to slow down, or underspeed. So in most flight conditions, it is true that selecting Beta or Reverse will merely tend to stretch the Reverse cable and not achieve anything except mis-rigging; the same as trying to Reverse in the hangar. But during stall practice in flight with idle power or deep into a landing flare – oh yeah! They’ll flatten right on out! Any lifting of the power levers in flight is expressly forbidden by the POH, and if they are not lifted they cannot be pulled back.

Again, my thanks to readers who have provided these good questions. Keep ‘em coming!

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