I am continuing more of my personal King Air “War Stories” for this month’s article.
Fuel Transfer and Crossfeed
It is exceedingly common for all of us to incorrectly use “Fuel Transfer” and “Fuel Crossfeed” interchangeably. However, the words actually refer to very different things. Correctly, Transfer should always refer to the movement of fuel from the King Air’s Auxiliary tank on one side into the Main tank on that same side whereas Crossfeed should refer to fuel going from one side’s Main tank to the opposite engine. We use Transfer on almost all of our flights in 90-series airplanes, except on shorter hops in the E90 and F90-series. We also use Transfer on the E90, F90, A100, B100, 200- and 300-series for longer flights. Crossfeed is hardly ever used, unless we are faced with a single-engine situation on the way to or from Europe, where no landing fields are nearby.
Here’s the point: The only way to know that Transfer and Crossfeed are actually working as they should is to periodically monitor the fuel quantity gauges. Let’s imagine that we got distracted in operating our 90, A90, B90, or C90 and simply forgot to turn on our Transfer Pump switches, left and right, after starting. We would of course get a “No Transfer” annunciator eventually to remind us to activate the pumps, right? Wrong!
Those annunciator lights only are enabled when the Transfer Pump switches are in the On position … or in the top, Auto, position for the later C90A and after models. Leave the pump switches off and you will never get a warning of your error!
In the E90, A100 and B100 models, if we forget to turn on the Aux Transfer switches, the “Aux Empty” lights on the fuel panel will never illuminate. It is easy to overlook the fact that as much as about 600 pounds of Aux fuel, 300 per side, is now useless. Do you realize that if the Main tanks go completely empty that the remaining Aux fuel becomes unusable even if we then turn on the Aux Transfer switches? That is because there will be no motive fuel flow from the Main tank to the Jet Transfer Pump on that side to initiate the transfer.
Thank goodness Beech automated the fuel transfer system on the 200- and 300-series, right? Since the opening of the motive flow valve to the jet pump is now automated and we no longer need to move a switch, it’s fool-proof, right? No, it isn’t. You see, if a shop rag fell into the Aux Tank filler and got sucked into the jet pump’s pickup port so as to block it, the system would never illuminate the No Transfer light – on the fuel panel on the 200-series and on the Caution Annunciator panel on the 300-series – because the pressure switch would still feel proper pressure in the jet pump’s discharge line even though the pressure there would come only from the motivating fuel flow with no Aux fuel being moved.
So, friends, here’s the takeaway: You MUST regularly examine both positions of your fuel quantity gauges – Total and Nacelle in the C90-type systems; Main and Aux in the 200-type system – to verify that the Aux Fuel level is properly decreasing. If you’re not doing this at least once every 30 minutes, please change your habit pattern!
As for Crossfeed, it is similar but not exactly the same. In the C90-style (and straight 100-style) of fuel system, the absence of the Fuel Pressure annunciator on the Receiving side, the side we are sending the fuel to, after we have turned off its own Boost Pump is a good verification that the Crossfeed valve has truly opened and that the feeding side’s Boost Pump is still functioning normally, supplying fuel pressure and fuel flow to the receiving side. The 90, A90, and B90 have actual boost pump Fuel Pressure gauges which easily indicate if the feeding side’s fuel is coming across.
Not so, however, on all models with an engine-driven boost pump: E90, F90-series, A100, B100, 200- and 300-series. Now, the receiving side’s Fuel Pressure annunciator will be extinguished due to the pressure coming from this side’s boost pump, regardless of whether the fuel that is creating that pressure has come out of the opposite nacelle tank – as it should be doing during Crossfeed – or has come, incorrectly, out of its own side’s nacelle tank due to a Crossfeed valve that failed to energize open or the feeding side’s Standby Pump not working. Remember that in all models except the 350, the Crossfeed annunciator only indicates that the normally-closed Crossfeed valve is receiving voltage, not that the valve has truly gone to the open position.
To emphasize the main point again: You must periodically observe the fuel quantity gauges on both sides to know with certainty whether your fuel Transfer and Crossfeed systems are functioning as you expect.
Now for the war stories: I found a model 200 once that was mis-wired such that the Crossfeed switch activated the incorrect Standby pump. When you wanted to send fuel left-to-right, it was going right-to-left. A 350 model I was in, one with less than 150 hours since new, was found to have its fuel quantity gauges wired “backward.” The left gauge read the right side and the right gauge the left. Geez!
Before I leave this topic, let me remind you of a “gotcha” that, I think, helped cause a brand-new C90GTi to sink in the Caribbean on its delivery flight to South America from the Wichita factory in 2012. Although the crew thought that they had given a request to fill all fuel tanks during their overnight stop in Florida, the FBO fueled only the Nacelle filler caps, thinking that this was the fuel order that was requested. How could the crew not have noticed that their quantity was low before takeoff?
This pilot was experienced in King Air 200s but was new to the C90-series. I speculate that he misread the fuel gauges. Instead of the “Total” and “Nacelle” readings he was actually seeing with the quantity selector switch Up or Down, I think he was expecting to see what he was used to seeing from his 200 experience: Up for “Main” and Down for “Aux.” Let’s see: 1,000 pounds in each side’s Main and 300 in each Aux…yes, that’s full fuel, about 1,300 pounds per side. But no, the total quantity was the 1,000 pounds per side that he was reading, comprised of 300 in the Nacelle and 700 in the Main. Not quite enough to make Aruba from Ft. Lauderdale.
The E90 We Wouldn’t Shut Down
Back in the early 1980s, a recurrent training customer of mine operated an E90 model for a lettuce grower with holdings in the Central and Imperial Valleys of California as well as near Hermosillo, Mexico. I had trained this pilot previously and knew him to be a competent professional. After our ground school sessions, the airplane’s owner had a lengthy trip scheduled for the next day. I agreed to work my flight training into this trip since there was scheduled to be three or four hours of waiting time down in Mexico before our return.
Bright and early we departed from John Wayne Airport (KSNA) in Santa Ana, flew to Bakersfield (KBFL) to pick up the owner, made a short hop and a stop in Imperial (KIPL) to pick up a couple of other passengers, then went on to Hermosillo (MMHO). We shut down, said goodbye to the passengers, took a short break, then completed our flight training briefing and headed for the airplane. We would be working within about a 50-mile radius of Hermosillo, VFR, with excellent weather. An hour or so into the flight the left Generator Out annunciator illuminated. We ran the checklist procedure – verified 28 volts on both side’s main buses, tried a generator switch reset – but to no avail. The left loadmeter still showed that the left generator was dead, carrying no load at all.
The student and I discussed our situation. If this was a generator failure only, meaning that the starter motor still worked, then it was reasonable that we could continue operating on one generator alone and complete the day’s mission. (No, we had no MEL, Minimum Equipment List, the only way we could legally carry on with only one generator. Remember that this was back in the early ’80s and the fears of enforcement repercussions were not the same as they are today. Plus, the weather was severe clear throughout our entire route.) On the other hand, if the starter motor was also inoperative, then we were stranded in Mexico until a replacement unit could be found, shipped in, installed and signed off. That could easily take many days.
So how do we determine if the starter is still able to operate? Here was our plan: At the safe altitude where we had been doing our air work – around 8,000 feet – we would shut down the left engine by placing its Condition Lever into Fuel Cutoff. We would not feather the propeller but allow it to windmill while the N1 slowed. Once the compressor speed stabilized we would conduct the “Air Start – Starter Assist” procedure. If the N1 spooled up normally then we would know that the starter was still functional. If it did not, however, we would then conduct the “Air Start – Windmilling Engine and Propeller” procedure and realize that if we wanted to get back home that day we could never shut that engine down on the ground!
With the engine shutdown and windmilling, we moved the Ignition and Engine Start switch to the Up position. Immediately, a loud, disconcerting noise filled our headsets and the N1 did not budge. Almost immediately the noise stopped and we turned the Starter switch off. We lowered the nose, picked up about 200 KIAS, turned on the Auto-Ignition switch and advanced the Condition Lever forward to Low Idle to conduct the windmilling air start procedure. This went well and soon we had both engines matched together as we headed back to the airport.
We had filled the outboard, main, tanks in Hermosillo before we took off on the training flight so had a significant amount of fuel onboard; would it be enough to complete all of our legs back to KSNA? It looked doubtful. However, it certainly looked like we had enough fuel to get back into the States, clearing customs in Calexico before heading on to Imperial. If we did that, at least the replacement starter-generator would not have to be shipped to Mexico and face the customs/import delays.
We landed and asked the tower/ground controller for permission to park on the far edge of the ramp since we needed to keep our left engine running. There were hardly any other airplanes around and permission was immediately given. My student went inside to contact the owner and tell him of our situation and ask him to expedite his return for departure. (No cell phones back then so he had to use a landline inside.) Meanwhile, I was going to stay with the airplane – shutdown on the ramp with the left engine still running at idle – and periodically turn on the battery to monitor oil pressure and temperature on that side. Thank goodness this was a PT6 that could idle for hours with no concern
When I switched the battery on after about 10 minutes, the oil temperature and pressure were fine but how come the right fuel quantity gauge was reading zero?! Hmmm, I had better do a current limiter check. I pushed both voltmeter buttons and the left side read battery voltage properly while the right side reads nothing … zero, nada, kaput. That means the right current limiter has been blown.
Oh, now it made sense to me! The broken starter-generator must have failed in such a way that when I tried using it as a starter, the current draw was much higher than normal. That high load on the right generator must have dropped its voltage so much that we heard the weird noise in the headsets. But almost immediately, the current limiter responded correctly to the excessive current by melting, by blowing … the noise ceased as the generator’s load came back into the normal range. On the way back to the airport with both engines running but with both the left generator and the right current limiter out simultaneously, the left Generator Bus was being fed only by the battery while the right side was being fed normally by the operating generator. Plus, the battery was no longer being charged.
But now, with the right engine shutdown we had no voltage at all on the right side since the blown current limiter prevented the battery from reaching that side.
Although gaining access to current limiters could be quite a chore in the earlier 90-series, by the time this particular E90 was manufactured, Beech had made the task much easier by relocating the limiters from their old position on the floor inside the cockpit pedestal to their new position under an easily-accessed panel between the pedestal and the co-pilot’s seat. I rolled back that area of carpet, removed the panel by releasing the two panel fasteners with a screwdriver … and then realized that I lacked a tool to undo the old limiter and replace it with one of the two spares that Beech nicely attaches to the bottom side of the access panel.
However, I hailed the fuel truck driver as he passed by and asked if he had a crescent wrench that I could borrow. (A half-inch socket wrench is the preferred tool but, hey, the old crescent wrench works in a pinch.) He had a wrench and within 15 minutes the old limiter was out, the spare was in, and voltage now appeared on both sides … and the right fuel quantity gauge again worked properly. (The right fuel panel receives its power from the right Generator Bus, also known as the right Main Bus. By the way, for you pilots who operate King Air models with the “Five Bus” electrical system – sometimes called the Triple-Fed System – this current limiter failure would not affect you in the same way. Plus, it would be highly unlikely to even happen since the current limiter has some protection during cross-starting.)
The pilot returned and informed me that the owner and the other passengers would be returning soon. They showed up nearly two hours later. The pilot met them, explained the situation, and escorted them to the cabin door while making sure they gave the spinning left propeller a wide berth. I momentarily feathered the left propeller to minimize the prop wash and exhaust smell as they boarded.
Off we go back to the good ol’ United States. The pilot did this trip regularly and personally knew the FBO and customs people along the way. He was able to explain why we had to keep the left engine running while we cleared customs and everyone he spoke with was quite accepting of that fact. When we got to Imperial, even the lineman was happy to add some fuel to both sides, while the left engine kept idling. (I was glad that the E90’s filler cap was close to the wing tip, not midway out as on the C90.)
Well after dark we completed the flight and shut down both engines back at KSNA. Mission accomplished. I am estimating that the left engine ran, nonstop, for over seven hours.
F90 Wingtip = Bonanza Wingtip
When I was still operating Flight Review, Inc. out of Hayward, California, I received a call from a fellow who owned and operated an aircraft salvage business in northern California. An owner-pilot whom I knew had wrecked his nice F90 on a dirt and gravel airstrip at a resort near the southern tip of the Baja Peninsula and the gentleman who called had purchased the salvage rights from the Mexican government. It turns out that an insurance inspector had written the airplane off as a total loss because of a cracked main spar yet the salvage guy had inspected it and determined that the crack could easily be repaired, so he got the airplane for the proverbial dime on the dollar.
The pilot had come in too low, caught the main gear on the berm of a road, ripped one gear off, and careened into the cactus beside the strip. To add insult to injury, he had also left the airplane there without making a report to the Mexican authorities. He flew back to the United States on a friend’s Cessna 414 so in the eyes of Mexico he was a wanted man.
After the salvage yard owner had inspected the wreckage, he concluded that it was reasonable to bid on the wreckage and then, with a couple of new propellers and the landing gear being locked down, he could safely fly it back to northern California, do a proper repair, and sell the airplane for quite a handsome profit.
This fellow had no King Air experience so he called me to ask for a day of my time. He wanted to (1) learn how to start the PT6s, and (2) learn some educated guesses on the speeds and fuel flows he could expect on the flight back home with the gear down.
We met at the conference room in the Beechcraft West facility at the Hayward airport and proceeded with the requested training. He was a sharp individual and I soon felt better that this “boondoggle” might work out better than I had first envisioned.
Near the end of the day, the fellow mentioned that the only thing preventing him from immediately leaving for Baja was the fact that he had not yet found an F90 wingtip to replace the left one that had been damaged when the gear collapsed. “Wait a minute,” I said. “You have already told me that the fuel vent system near the wingtip, and the tip itself, has been damaged so that you do not plan to add enough fuel to have it near the tip. All you really need is a tip for aerodynamic purposes, not one that fully complies with the F90 design. Right?”
“Yes, exactly!” was his reply. “Then why not use one of the Bonanza tips you have at the salvage yard?” I asked.
“What?!” he queried. “It wouldn’t fit!” “Yes, it will,” I said. “It’s the same size.”
“No way!” With measuring tape in hand, we proceeded to walk into the Beechcraft West hangar and, by luck, found both an F90 and a V35B there. Out came the tape measure and – voila! – an exact match. I have rarely seen an individual as happy as this fellow was at that moment! His wingtip search was over.
If you have not known of this before, learn it now: The wing section outboard of the nacelle on a King Air has the exact same shape and size as the wing on Bonanzas, Barons, Dukes, Twin Bonanzas and Queen Airs. Different spar strengths? Different fuel cells? Different aileron attachment and design? Different wing bolt design and installation in some? Different wing tip extension lengths, the length outboard of the ailerons? Yes, to all of these possibilities, but the basic wing airfoil shape and size … identical for all.
Until next month … and we’ll get off this War Story detour for a change. Have you enjoyed the stories? There are more to come.