In 1977 I had left Beech Aircraft Corporation’s Training Center in Wichita and transferred to the factory-owned Beechcraft West retail facility in Hayward and Fresno, California, as an aircraft salesman. Although Hayward would be my home for the next 10 years, my first months were mostly spent in Fresno. Why? Because Larry Hall, the head honcho in Fresno, was temporarily managing both facilities and he wanted to give me “under his wing” guidance as I made the transition from the factory to the field. It wasn’t too long before I found that I was not cut out to be a salesman, and in 1979 I started Flight Review, Inc. – a King Air and Duke on-site training operation that I managed for 21 years.
Larry was a good guy and mentor, at least it seemed that way to me. He is the one who taught me to cruise climb a Baron at full power and 500 fpm and just accept whatever speed that yielded. Scientific? Good for all situations? No. But it certainly worked well for a lot of our Fresno-Hayward flights.
Larry had sold – and maintained in which I had helped – a 1977 King Air 200 (serial number BB-294) to the Government of Sabah, a Malaysian state on the island of Borneo. He believed (correctly!) based on my less-than-stellar sales performance that he could make better use of my talents by getting me involved with the delivery of this airplane to Borneo and the subsequent crew training that would be needed there. Thus, began a most interesting and unusual five months of my life.
Larry contracted with a fellow whose business was ferrying airplanes across the Pacific. This gentleman had lots and lots of ferrying experience but always in single and twin-engine piston, unpressurized airplanes. Since he had never flown a turboprop and I had never executed a Pacific crossing, it was a symbiotic combination! What could go wrong?
To make the flight from Oakland, California, to Honolulu, Hawaii, the King Air 200 needed about 350 more gallons of fuel on top of the 544 normal gallons. Our ferrying friend had worked often with a maintenance facility located on the Oakland airport (KOAK) in the San Francisco Bay area. He arranged for them to do the extra tanking for our flight. The plan was to add three aluminum, rectangular tanks – one in front of the main spar and two behind, all securely mounted to the seat tracks – to accommodate the desired extra fuel. The seats that had occupied the space where the tanks would go would be secured in the back of the cabin and in the baggage area.
How would the fuel in these extra tanks get to the engines? The tanking organization asked for my input and I came up with this idea: The crossfeed line was the only fuel-containing line that was available under the floorboards in the cabin. I thought that we could install a T-fitting into this line that would allow our cabin fuel to feed to both engines.
The three cabin tanks were plumbed in parallel so that any or all could feed to the T-fitting on the crossfeed line. We had an electric boost pump installed in the line between the tanks and the T-fitting to ensure that the fuel from the cabin would have priority over any fuel coming from the wings. Remember that the crossfeed line feeds directly to the engines and that a checkvalve prevents this fuel from entering a tank.
The Normally Closed (NC) crossfeed valve is located in the left wing, so when our cabin fuel was introduced into the T-fitting, it would initially feed only to the right engine. Once that flow was verified, we could then open the crossfeed valve and allow cabin fuel to feed to both engines.
But, wait a minute! To open the crossfeed valve in a 200 (and F90 and 300-series King Airs) requires moving the crossfeed switch left or right and this also turns on the feeding side’s electric standby pump. If the pressure output of this pump is greater than the pressure of the cabin fuel connected to the T-Fitting then the cabin fuel would not be utilized. Instead, the fuel from the side of the operating standby boost pump would supply both engines and probably even send fuel into the ferry tanks.”
So, the question I faced was, “How do I open the crossfeed valve without activating the standby pump?”
Simple: Pull the pump’s circuit breaker beneath the fuel panel. Oops that won’t work. You see, in serial numbers before BB-1098, the standby pumps were “hot-wired,” receiving power from two 5-amp, parallel-wired fuses off the Hot Battery Bus in addition to the left or right pump’s circuit breaker (CB) that received power from the #3 or #4 Dual Fed Bus. Solution? Remove those two 5-amp CBs before we commenced operation. Afterall, we were going to have an approved ferry permit anyway, authorizing our procedures, right? Plus, Beech removed the hot-wiring in the later airplanes anyway.
As the tank plan was being discussed with the ferry tank company that would install it, a discussion arose about the venting of the tanks. As they had done hundreds of times before in unpressurized singles and twins, they planned to simply install a vent line from the ferry tank combination through a fitting in the belly’s skin to the ambient, outside air.
I said, “Wait a minute! That won’t work! Remember that our cabin is pressurized. If the inside of those tanks is subjected to ambient air pressure while the outside is subjected to cabin pressure – 6 psi greater – they will collapse!”
The tanking people assured me that I was mistaken; that their tanks were strong enough to handle the pressure differential. I was quite skeptical of their belief but the project went forward to the installation and testing phases.
I accepted the new airplane at the Wichita factory and after a thorough test flight there flew it to Beechcraft West at the Hayward airport for temporary storage. Knowing that the crossfeed line would be cut open to install the T-fitting, I wanted to have the fuel quantity on board as low as possible, so there would be less to defuel before opening the line.
On the day I was to make the short hop from Hayward to Oakland to begin the tanking process, I discovered that the “helpful” fuelers had topped off both side’s main tanks. Darn! I was told that the tanking company was not equipped to accept that much Jet-A for temporary storage so I should burn it off before arriving at KOAK. “It’s a tough job but someone has to do it!” I chuckled, as I envisioned flying up and down the lovely northern California coast for a few hours at low altitude and high power, burning up the unwanted fuel.
About the time I passed the Golden Gate bridge heading north, this thought came to me: All I really need to do is burn off the fuel on the right side. Since the crossfeed valve is in the left side, the left fuel cannot find its way into the crossfeed line section in the cabin unless the valve is open. When that insight registered – and with only myself on board – I moved the crossfeed switch from the center position to the left. This action opened the crossfeed valve and turned on the right standby pump. As expected, the right main fuel was now feeding both engines while the left fuel was no longer being consumed.
Wow! Look at the fuel quantity gauge go down! At my cruise altitude of 1,500 feet I was burning about 400 pounds per-hour, per-engine so in an hour I had about 1,200 pounds remaining on the left side and 400 on the right. The imbalance limit on the 200-series is 1,000 pounds so I started heading for Oakland. Periodically I would turn off the autopilot and see how much aileron trim I needed to handle the heavier left wing. Surprisingly, little trim was required. As I slowed for landing, I cranked in more trim as needed but even with the 1,000-pound difference and at 100 knots, I never needed more than half of the available trim. What did catch me by surprise – and I have mentioned this in my book – was how much the airplane wanted to turn left when taxiing. The extra weight on the left main tires surely wanted to pull the plane to the heavier side!
In a week or so the tanks were installed, the vent line was fitted from the tanks through the belly skin, the electric boost pump – on a wooden board fastened to the left seat tracks in front of the spar – was plumbed with the proper fuel lines and wired with power … we were ready for a test flight. Thirty-five gallons had been added to each of the three, interconnected tanks and the mains had again been filled. The filler cap on each of the ferry tanks would be left off until we got to altitude, allowing cabin air to freely flow in and out of the tanks. We would be operating normally, consuming fuel from the main tanks, until we were in cruise and ready to test.
This time we went up to 17,500 feet – on a clear day, flying VFR – and were fully pressurized to 6.0 psid. Before opening the manually operated valve to permit the ferry fuel to reach the T-fitting, one of the two “tank guys” in back started installing the tank caps. These were the metal, screw-on type. I heard a “clank” and some metal-moving-on-metal sounds as the first cap was screwed tight. Soon the second cap made the same sounds that I could hear. Remember, since the three tanks were interconnected, cabin air was still inside and outside all of the tanks.
Finally, I heard the last “clank.” However, this time it was immediately followed by a loud string of expletives and a yell of “Take it off! Take it off!” coming from the other installer in back. As soon as the inside of the tanks was no longer subjected to cabin air but started to decrease toward the ambient air at 17,500 feet to which they were vented, the three big box-shaped tanks collapsed as if they were made of tissue paper! On the way back to Oakland I had to bite my tongue to keep the “I told you so!” from leaking out. Six pounds pushing on one side more than the other against every square inch of aluminum adds up to a lot of destructive force.
A meeting was held back in the tanking company’s office to discuss the failure. I proposed the following solution: Retain the existing design but with one small addition: a one-half psi relief valve between the tanks and the cabin. This one-way valve would allow cabin air to flow into the ferry tanks and then go overboard through the belly vent line. No kerosene fumes would ever reach the cabin. The differential pressure between the inside and outside of the tanks would never exceed one-half psid. Also – and this would have to be proven on a further test flight – I was quite certain that the 5.5 psi difference between the ferry fuel and the wing fuel would be sufficient to feed fuel from the cabin tanks into the crossfeed line without needing to run the ferry system’s boost pump.
A week or two later we were advised that they were ready for a second test flight. This time we not only filled the mains but also put 25 gallons in each aux tank, as well as the 35 gallons in each ferry tank. Back in 1978 I had not yet learned the important “trick” of burning a couple of hundred pounds out of the mains before transferring to the aux tanks. So, we took off and climbed to altitude burning main tank fuel that was being replenished from the aux tanks. Once this was confirmed to be normal, we then pulled the left and right aux transfer circuit breakers to shut down the normal transfer. Next the three caps were screwed onto the tanks and, as expected, nothing bad happened. We now opened the valve to allow ferry fuel to feed into the crossfeed line.
How did we know if it was working? Was the right engine actually burning the ferry fuel or was it still using fuel from the right main? The only way to tell was to let enough time pass to see if the right main quantity was or wasn’t decreasing. In about 30 minutes we all agreed that the right main quantity was not dropping. Yay! The system was working as planned; and we had not turned on the ferry system pump. That 5.5 psid pressurization-provided “shove” was all we needed.
Lastly, I pulled the right standby pump CB – we had previously removed the hot battery bus fuses for the right standby pump – and moved the crossfeed switch to the left. This powered the crossfeed valve to the open position but did not activate the standby pump. Doing this provided a path for our ferry fuel to reach the left, as well as right engine.
Again, a half-hour or so of waiting confirmed that none of our main fuel was being consumed. Success! A plane full of happy people headed back to Oakland.
By the way, I understand that the military and other operators use a completely different ferry fuel system in the 200- and 300-series of King Airs. Instead of feeding into the crossfeed line I believe fuel flows from the cabin into both side’s aux tanks and from there gets transferred normally into the main tanks before being consumed. Can any of my readers confirm this and explain exactly what is involved in the installation? Specifically, how does the venting system work and how does the fuel get to the aux tanks?
The system that I designed seems to be simple with only one fitting on one line necessary. It requires very little airplane modification: The T-fitting and the overboard vent. Am I missing something? Is there some lurking danger in this design of which I am unaware? It certainly worked perfectly all across the Pacific!
Please email or phone me directly at firstname.lastname@example.org / (602) 625-9132 if you have any information to share concerning other ferry tank arrangements. I will give you credit and acknowledgement if I include your information in a future article. Thank you!
To be continued next month …