Ch.16 - The Next Lightning (Apr 1943)
20 April 1943
Burbank, California, USA
Beneath the elaborately painted canvas awning which stretched over the entirety of the Lockheed production facility, Ralph Virden walked among the rows and rows and freshly completed P-38’s. In the past few days the first few dozen P-38H’s had started to roll off the assembly floor and were now having their final checks and getting all of the little details added that they would need before delivery to the Army Air Force.
Today, though, Ralph would be flying AAF serial number 42-13566 which was the last of nine P-38G-15-LO’s that Lockheed kept as testing and development planes. The airplane had been part of the P-38H development group and so had previously been upgraded to P-38H-1-LO standards but had also recently been upgraded even further.
The modifications to meet P-38H-1-LO standards were extensive and included:
The new heating and ventilation system was a great improvement over the previous models. Ralph had been involved with some of the testing several weeks prior after the order came down from the Air Corps to replace the existing system with one similar to that used in a P-39. Where the old heater system drew air through blast tubes on the upper nacelles and ran around the hot exhaust pipes to heat the air before ducts brought it under ram pressure through the center wing section to the cockpit, the new system consisted of a simple air-box placed directly behind the coolant radiators about half-way along the center wing span. The air boxes collect hot air from the radiator exit and pipe it directly into the cockpit with one vent on the cockpit floor between the rudder pedals and another vent stretching around the forward dash to blow hot air directly onto the front windshield to prevent any fogging or icing at high altitude. The engineers kept the old blast heat in place to continue providing heat to the armament compartment while the old cockpit floor heat duct was terminated in the radio compartment to reduce fogging on the rear canopy and minimize the risk of icing to the hydraulic regulator.
Cockpit ventilation had also been improved by moving the old cold-air inlet from the left wing-root farther outboard and mirroring the setup of the right side. The new vent inlets were now integrated into the leading edge slots and consisted of three inch flaps above the coolant radiator which could drop to form a small scoop up to three inches down into the air stream. The new heating and cooling vents were controlled together by two small levers on either side of the cockpit. The lever on the left controlled the mix of hot and cold to the floor vent, while that on the right changed the airflow mixture going to the windshield vent.
In testing at the end of March, Tony LeVier had reported flying an airplane with the new heat/vent system at 35,000 feet with an Outside Air Temperature of around -65°F (-54°C) for one hour and was able to keep the cockpit above 35°F (2°C) the entire time. At lower altitudes of between 25,000 and 30,000 feet Ralph himself was able to fly the airplane for more than two hours and maintain the cockpit at a cozy 60°F or warmer.
Another modification, made possible by the new heating system and the removal of the old floor heat duct, was the rearranging of the trim tab control wheels to a single location on the raised center console directly between the pilot’s legs. A transverse wheel at the rear controlled aileron trim, a longitudinal wheel to the left for elevator trim, and the same turn knob front and center for rudder trim control as always.
Not all of the desired improvements were available or ready by the time H-model production started either because of continued development or due to lagging production from the required sub-contractors; so, even though the Block-1 P-38H’s were only just starting to come off the line the production teams were already preparing for Block-5 production and were starting to test the final round of improvements for would be called Block-10.
The Block-5 airplanes were scheduled to replace the old electrical fuses from their hard to reach locations in the nose at the rear of the armament compartment and in the forward landing gear bay with a new electrical circuit breaker system in the cockpit to the pilot’s right directly in front of the flap control lever. The breaker system had already been tested in three different configurations on airplanes #41-13563, #42-13564, and #42-13566 and the final production models were expected to use the breaker boxes and arrangement from #566.
This new electrical system was, in turn, the pre-requisite for the improvements being worked on upstream for the planned Block-10 airplanes which would include a completely revised engine switch box including new unified energizer/mesh switches for each engine, an automatic engine primer combined with the oil-dilution switch, simplified engine master switches, and a new electro-mechanical fuel management system with automatic fuel booster pump switching.
Ralph knew from talking with Tony LeVier that the fuel management system, in particular, would be a great improvement but from his personal experience he was more excited about the starter controls. Flying the variations of the P-38 since the old YP-38’s nearly three years prior the biggest hassle for him had always been the lack of a third hand to get the engines turning.
Sitting down into the cockpit of the modified #566, Ralph reviewed the new controls before going through the revised pre-flight checklist and start up procedures. The most obvious visible difference is the new electric fuel control box on the lower left of the instrument panel where the old gun charging selector knob used to be and conveniently placed directly below the fuel gauges. This box was dominated by a single large four-position free-turning dial with each 90° position corresponding to a tank selection (clockwise from the 12 o’clock position): MAIN, RESERVE, EXTERNAL, and OUTER WING. Above this knob, at approximately the 10 o’clock and 2 o’clock location were two small fuel level check/warning lamps; while directly below it were two Fuel Selector Override switches, one for each side.
Looking down and to his left, next to the seat behind the landing gear lever, Ralph noted that the old manual fuel selector valves were still installed with a fifth position, CROSS-SUCTION between the MAIN and RESERVE positions. Behind these two valves was the Auxiliary Fuel Control switch box witch had the two Fuel Booster Pump Speed Control switches and a single Outer Wing Tank Low Level Check button.
Directly in front, beyond the offset yoke and at the bottom of the instrument panel, was the Main Switch Box. The new box had been re-organized to simplify start up and basic operations. The circular Ignition circuit was more-or-less the same with a central Ignition Master switch and two individual engine ignition turn switches which control the individual magnetos on each side.
Left of the Ignition control were the two new Fuel Pump/Dilution switches, one for each engine. These now operate by being OFF when all the way down, ON when locked in their center position, and when pressed all the way forward act as the Oil Dilution Switches which automatically return to ON when released.
These switches were directly related to the two starter switches. Where on previous airplanes there was a switch to energize the starters and separate switch to engage the starters, with one engine being activated when the switches were down and the other when the switches were up; the new switches now each controlled their own engine. When down the starters were OFF, when pushed halfway forward they energized the starters and (so long as the Fuel Pump switches were ON) automatically primed the engine, and when forced all the way forward through a resistant stop they engaged the starters. These new switches were designed to simplify engine start and enable simultaneous startup of both engines, something that was impossible with the only starter switches.
To the right of the starter switches was the Pitot Heat switch, the Position Lights switch, the Landing Lights switch, and finally the battery switch—all of which were simple OFF/ON type switches. Beyond this was the same Voltmeter that was installed.
On the front of the Main Switch Box were now only six switches in three circuits and two round rheostats. Each circuit had two switches for Left and Right sides and were, from Left to Right: Oil Flap Override, Coolant Flap Override, and Intercooler Shutter Override. These each operated the exact same way and enable the pilot to manually open or close the respective flaps and exit shutters separate from the automated system installed in all H-Model airplanes. The override switches were at AUTO when centered and the automatic system could control the flaps. Moving the switch up would override the automated system fully close the respective flap or shutter and, conversely, moving the switch down would override the system and fully open the appropriate flap or shutter.
Farther to the right, below the Voltmeter were the Cockpit light Rheostat knob and the Gunsight light Rheostat knob. There had been talk about moving the gunsight rheostat to the control column but from what Ralph understood this modification had been put on hold because there was a rumor of replacing the obtrusive off-set column with one of a different design.
Contrary to Air Force request, the individual Generator switches were kept as they had been on the lower Instrument Panel as Lockheed test engineers had determined it is easier for the pilot to check the generator when the switch is directly below its associated Ammeter.
After securing his harness and familiarizing himself with the fuel and starter controls, Ralph started the pre-flight checks and prepared to start the engines. He would be running this test without a battery cart, so he first switched the Battery switch up to the ON position and confirmed the Voltmeter was registering current.
Following the new procedures, Ralph’s first job was to test that the Low Fuel Level Warning lights were functioning by pressing directly on the lights themselves and forcing them deeper into their sockets. Both lights glowed amber, which meant the bulbs were good and the warnings working.
The next series of checks were unchanged from previous P-38 models, checking Oxygen pressure, moving the throttles ¾ of an inch open, setting propellers to INC. RPM, propeller constant speed switches to AUTO CONSTANT SPEED, propeller circuit breakers ON, and mixture was at IDLE CUTOFF for both engines. After that, Ralph checked that both oil radiator flap override switches were in AUTO, both coolant flap override switches were in AUTO, and both intercooler shutter override switches also in AUTO before switching on both generators and the inverter switch to his right.
Since he would be flying with external Drop Tanks today as part of the fuel system tests he also turned the Bomb selector switches (with also controlled the drop tanks) ON and made sure they were SAFE just in case he needed to jettison them on takeoff due to an emergency.
Ralph ensured the Ignition Master switch and both engine ignition switches were OFF then called out of the open canopy for the ground crew to turn over the propellers while he set about checking the new fuel system. He first moved the old manual tank selectors to the recommended RESERVE position and checked that the Booster Pump Speed Controls were both at NORMAL. He followed that with confirmation that the Fuel Selector Override switches were both in the down, OFF, position and then turned the electric fuel selector knob to the 9-o’clock OUTER-WING position and moved both Fuel/Dilution switches to ON.
His fuel pressure gauges jumped up to hover between 6 and 8 pounds per square inch pressure, perfect. A flick of his fingers moved the Speed Control switches to EMERGENCY and the fuel pressure jumped up even farther, to about 18 pounds per square inch. After returning the speed controls to NORMAL, Ralph pressed the Outer Wing Tank Low Level Check Button and was happy to see that neither low level warning lights lit up, indicating there was at least five minutes of fuel in the tanks.
He then repeated the fuel pressure tests for the MAIN, RESERVE, and EXTERNAL to confirm proper operation of each of the new individual booster pumps. Although there was no way to gauge the fuel level in the external tanks, the MAIN and RESERVE tanks each had their own fuel gauges so there was no need to test levels through a separate procedure as there was with the outer-wing tanks. He left the selector on RESERVE and made one final confirmation that the speed selectors were at NORMAL.
Once he received the OK from the ground crew, he flipped on the Ignition Master Switch. Now was when he would test the new starter system and confirm that it allows both engines to start simultaneously as intended. With his left hand ready on the mixture controls, Ralph reached his right hand past the yoke, turned both Engine Ignition Switches to BOTH to equally share the load between the magnetos, and pressed both Left and Right Starter switches until he felt a resistant stop, indicating they were in the center ENER (Energize/Prime) position.
A familiar electrical hum started from both sides and starting building into a whining crescendo. After a few seconds the crescendo peaked and Ralph forced the starter switches through the stop until they were fully forward. The electric whine dropped in pitch but with a series of short pops the propellers jerked around in a few partial revolutions before both engines sparked to life. Ralph pushed the mixtures to AUTO RICH and the comforting roar of the big V-12’s filled his ears.
He released the starter switches, letting them spring back to their resting places, and watched the oil pressure gauges to confirm both engines were fully smooth and operational. As he let the engines warm up he made a note of the ease and success of the new startup procedure. He also took the opportunity to test his radio and hydraulic systems.
Once the engines had warmed up sufficiently, he increased to 2300 RPM and tested the propeller controls—finding he had to fine tune the right propeller a little to synchronize it with the left. Then it was the standard magneto checks, generator tests, as well as testing the radiator flaps and intercooler shutters before throttling each engine up to take off levels briefly to confirm the turbos were working and to adjust the throttle lever friction.
He was ready for takeoff.
* * *
Ralph’s flight tests today, with the starter procedure out of the way, was entirely related to fuel management. He was to test each tank through the electric control, the manual control, and to test cross-feeding between sides for all tanks, including the outer wing tanks which were now fully integrated into the main fuel tank selector valve.
His first tests were simply to go through the four different tanks with both engines drawing from their own side. The procedures for normal operation were very easy. He simply needed to confirm the Fuel Selector Override switches were both in the down, OFF, position, then turn the single fuel tank selector dial. Doing so changes a series of actuators on both sides to open fuel flow for the the selected tank. So, with both overrides OFF, moving the one free-turning knob to RESERVE switches both engines to draw from their respective Reserve Tanks and an electrical contact automatically turns on the Reserve tank booster pumps.
The way the engineers explained it to Ralph was that when the overrides are in the OFF position they activate the electrical circuits for the electrical fuel management systems and close a master valve actuator off the manual valve output line. The master actuator is set up so that when there is a steady low current flowing into it the valve remains closed and when the current ceases the valve automatically opens. The individual tank valve actuators--which are on bypass lines around the manual valve--are the opposite, so that their natural state is to be fully closed but when a tank is selected the valves for that tank remain open as long as there is current into the actuator. Therefore, the tank selector dial has a total of six contactors for each position—two to maintain current to the valve of the selected tank on each side, two which open the current to the fuel booster pumps on the selected tanks, and two more which connect the selected tanks to the Low Level Warning Lights above the selector knob.
While this system means that there is a constant low electrical drain to keep the master valve closed and the selected tank valves open, it does ensure that in the event of electrical failure or even just failure of the electric fuel management system all tank valves on the bypass lines automatically close and the master opens allowing fuel to flow from the old manual valves to the pilot’s left. Likewise, moving the override switch for one side to ON interrupts the current for the entire circuit on that side which causes all associated valves to close and that side's master to open and fuel can then be managed by the manual valve.
For the flight the airplane had been only partially fueled so Ralph could test not only the fuel tank selection but also the low level warning. This system, which was just an expansion of that put in place for the outer wing tanks in previous models, was designed to automatically ignite the Low Level Warning lights for the selected tanks on each side when there was only 5-6 minutes of fuel remaining in the tank, based on normal consumption at Maximum Cruise, or about six gallons of usable fuel. The idea was to give an obvious and visible warning to the pilot that his selected tanks were about to run dry with enough time for him to switch to a tank with more fuel. The hope was that this would dramatically reduce the number accidents resulting from fuel starvation when a pilot failed to switch tanks.
Once the tests for normal operation were complete, Ralph start testing the ability properly draw fuel across the airplane by cross-feeding the fuel from a single tank on one side to the engine on the opposite. To do this, he first moved the tank selector dial to desired tank, then turned the manual valve for the engine which would cross-feed to the CROSS SUCTION position, then simply switch the Fuel Selector Override for the cross-feeding engine to ON.
Ralph moved the tank selector dial to EXTERNAL and with his left hand moved the right engine manual fuel valve to CROSS SUCTION. With that set, he just reached forward and moved the right side Fuel Selector Override switch up to ON. He flew in this condition for ten minutes to confirm the cross-feed was working properly, then turned fuel selector dial from EXTERNAL to OUTER WING. The change happened without difficulty and he was relieved to discover that both engines continued run without interruption.
He flew on the left outer wing tank for about 25 minutes before the left Low Level warning light started to glow a soft amber. Ralph then switched on to the MAIN tanks, with the right engine still in CROSS SUCTION. He made a note of when the warning light turning on—when he landed the test engineers would check the fuel remaining in the tanks and those tanks when he switched off when the light came on should each have around five gallons of fuel.
Ralph repeated this process, draining the left MAIN tank down, before he switched the right side Fuel Selector Override back down to OFF. He ran on both MAIN tanks until the left warning light once again started to glow, it being drained before the right because of running both engines off it for a while. When the waning light turned on, he turned left manual selector valve to CROSS SUCTION and flicked the left override ON. Immediately the warning lamp turned off as fuel began to flow to the left engine from the right MAIN tank for a moment before he turned the selector dial down to EXTERNAL.
The plane flew for a good 10 minutes on the right drop tank before Ralph once more made the switch to the OUTER WING. This time, the fuel flowed form the right wing to right engine and through the cross suction valve to the left. He flew like this for another 20 minutes before the right low level warning light began to glow and he was forced to make a switch to run both engines from the right MAIN.
Half an hour later the right low level warning once more turned on and Ralph knew the flight testing was done. He turned the selector RESERVE, flicked the left override OFF, and turned back toward Burbank.
* * *
Later that day the engineers reported back the fuel levels remaining in each tank. Ralph had only run each drop tank for 10 minutes, they started with only 50 gallons each and after landing it was discovered that left tank had 31.4 gallons and the right 30.7 gallons which meant they each lost just under twenty gallons—exactly as expected for running both engines for ten minutes at 2300 RPM and 35 in/Hg. manifold pressure.
Both MAIN tanks and both OUTER WING tanks had been run down until the low level warning light came one and they were found to have (from left to right) 5.6, 5.2, 6.1, and 5.8 gallons. The RESERVE tanks were used to fly in and were not run dry but had 14.2 gallons in the left and 12.7 gallons in the right.
In the end, Ralph and the engineers all agreed that the test was a resounding success. If they could get the new switches and new fuel management system produced in bulk and be allowed permission to interject them into the production they could only hope these improvements could arrive to the front by mid-summer.
Burbank, California, USA
Beneath the elaborately painted canvas awning which stretched over the entirety of the Lockheed production facility, Ralph Virden walked among the rows and rows and freshly completed P-38’s. In the past few days the first few dozen P-38H’s had started to roll off the assembly floor and were now having their final checks and getting all of the little details added that they would need before delivery to the Army Air Force.
Today, though, Ralph would be flying AAF serial number 42-13566 which was the last of nine P-38G-15-LO’s that Lockheed kept as testing and development planes. The airplane had been part of the P-38H development group and so had previously been upgraded to P-38H-1-LO standards but had also recently been upgraded even further.
The modifications to meet P-38H-1-LO standards were extensive and included:
- New Allison F-17 engines (V-1710-89/91)
- A new War Emergency Power setting offering 60 in/Hg. of boost
- Automated Coolant and Oil Radiator flaps
- Automated Inter-cooler exit shutters
- A new cabin heater and ventilation system
- Minor improvements to the cockpit switch layouts
- Re-designed magazine and ammunition feed for the AN/M2 machine guns
- Removal of the spent cartridge ejection chute control from the cockpit
- Removal of the manual gun charging handle from the cockpit
- Combination of machine gun and cannon switches
The new heating and ventilation system was a great improvement over the previous models. Ralph had been involved with some of the testing several weeks prior after the order came down from the Air Corps to replace the existing system with one similar to that used in a P-39. Where the old heater system drew air through blast tubes on the upper nacelles and ran around the hot exhaust pipes to heat the air before ducts brought it under ram pressure through the center wing section to the cockpit, the new system consisted of a simple air-box placed directly behind the coolant radiators about half-way along the center wing span. The air boxes collect hot air from the radiator exit and pipe it directly into the cockpit with one vent on the cockpit floor between the rudder pedals and another vent stretching around the forward dash to blow hot air directly onto the front windshield to prevent any fogging or icing at high altitude. The engineers kept the old blast heat in place to continue providing heat to the armament compartment while the old cockpit floor heat duct was terminated in the radio compartment to reduce fogging on the rear canopy and minimize the risk of icing to the hydraulic regulator.
Cockpit ventilation had also been improved by moving the old cold-air inlet from the left wing-root farther outboard and mirroring the setup of the right side. The new vent inlets were now integrated into the leading edge slots and consisted of three inch flaps above the coolant radiator which could drop to form a small scoop up to three inches down into the air stream. The new heating and cooling vents were controlled together by two small levers on either side of the cockpit. The lever on the left controlled the mix of hot and cold to the floor vent, while that on the right changed the airflow mixture going to the windshield vent.
In testing at the end of March, Tony LeVier had reported flying an airplane with the new heat/vent system at 35,000 feet with an Outside Air Temperature of around -65°F (-54°C) for one hour and was able to keep the cockpit above 35°F (2°C) the entire time. At lower altitudes of between 25,000 and 30,000 feet Ralph himself was able to fly the airplane for more than two hours and maintain the cockpit at a cozy 60°F or warmer.
Another modification, made possible by the new heating system and the removal of the old floor heat duct, was the rearranging of the trim tab control wheels to a single location on the raised center console directly between the pilot’s legs. A transverse wheel at the rear controlled aileron trim, a longitudinal wheel to the left for elevator trim, and the same turn knob front and center for rudder trim control as always.
Not all of the desired improvements were available or ready by the time H-model production started either because of continued development or due to lagging production from the required sub-contractors; so, even though the Block-1 P-38H’s were only just starting to come off the line the production teams were already preparing for Block-5 production and were starting to test the final round of improvements for would be called Block-10.
The Block-5 airplanes were scheduled to replace the old electrical fuses from their hard to reach locations in the nose at the rear of the armament compartment and in the forward landing gear bay with a new electrical circuit breaker system in the cockpit to the pilot’s right directly in front of the flap control lever. The breaker system had already been tested in three different configurations on airplanes #41-13563, #42-13564, and #42-13566 and the final production models were expected to use the breaker boxes and arrangement from #566.
This new electrical system was, in turn, the pre-requisite for the improvements being worked on upstream for the planned Block-10 airplanes which would include a completely revised engine switch box including new unified energizer/mesh switches for each engine, an automatic engine primer combined with the oil-dilution switch, simplified engine master switches, and a new electro-mechanical fuel management system with automatic fuel booster pump switching.
Ralph knew from talking with Tony LeVier that the fuel management system, in particular, would be a great improvement but from his personal experience he was more excited about the starter controls. Flying the variations of the P-38 since the old YP-38’s nearly three years prior the biggest hassle for him had always been the lack of a third hand to get the engines turning.
Sitting down into the cockpit of the modified #566, Ralph reviewed the new controls before going through the revised pre-flight checklist and start up procedures. The most obvious visible difference is the new electric fuel control box on the lower left of the instrument panel where the old gun charging selector knob used to be and conveniently placed directly below the fuel gauges. This box was dominated by a single large four-position free-turning dial with each 90° position corresponding to a tank selection (clockwise from the 12 o’clock position): MAIN, RESERVE, EXTERNAL, and OUTER WING. Above this knob, at approximately the 10 o’clock and 2 o’clock location were two small fuel level check/warning lamps; while directly below it were two Fuel Selector Override switches, one for each side.
Looking down and to his left, next to the seat behind the landing gear lever, Ralph noted that the old manual fuel selector valves were still installed with a fifth position, CROSS-SUCTION between the MAIN and RESERVE positions. Behind these two valves was the Auxiliary Fuel Control switch box witch had the two Fuel Booster Pump Speed Control switches and a single Outer Wing Tank Low Level Check button.
Directly in front, beyond the offset yoke and at the bottom of the instrument panel, was the Main Switch Box. The new box had been re-organized to simplify start up and basic operations. The circular Ignition circuit was more-or-less the same with a central Ignition Master switch and two individual engine ignition turn switches which control the individual magnetos on each side.
Left of the Ignition control were the two new Fuel Pump/Dilution switches, one for each engine. These now operate by being OFF when all the way down, ON when locked in their center position, and when pressed all the way forward act as the Oil Dilution Switches which automatically return to ON when released.
These switches were directly related to the two starter switches. Where on previous airplanes there was a switch to energize the starters and separate switch to engage the starters, with one engine being activated when the switches were down and the other when the switches were up; the new switches now each controlled their own engine. When down the starters were OFF, when pushed halfway forward they energized the starters and (so long as the Fuel Pump switches were ON) automatically primed the engine, and when forced all the way forward through a resistant stop they engaged the starters. These new switches were designed to simplify engine start and enable simultaneous startup of both engines, something that was impossible with the only starter switches.
To the right of the starter switches was the Pitot Heat switch, the Position Lights switch, the Landing Lights switch, and finally the battery switch—all of which were simple OFF/ON type switches. Beyond this was the same Voltmeter that was installed.
On the front of the Main Switch Box were now only six switches in three circuits and two round rheostats. Each circuit had two switches for Left and Right sides and were, from Left to Right: Oil Flap Override, Coolant Flap Override, and Intercooler Shutter Override. These each operated the exact same way and enable the pilot to manually open or close the respective flaps and exit shutters separate from the automated system installed in all H-Model airplanes. The override switches were at AUTO when centered and the automatic system could control the flaps. Moving the switch up would override the automated system fully close the respective flap or shutter and, conversely, moving the switch down would override the system and fully open the appropriate flap or shutter.
Farther to the right, below the Voltmeter were the Cockpit light Rheostat knob and the Gunsight light Rheostat knob. There had been talk about moving the gunsight rheostat to the control column but from what Ralph understood this modification had been put on hold because there was a rumor of replacing the obtrusive off-set column with one of a different design.
Contrary to Air Force request, the individual Generator switches were kept as they had been on the lower Instrument Panel as Lockheed test engineers had determined it is easier for the pilot to check the generator when the switch is directly below its associated Ammeter.
After securing his harness and familiarizing himself with the fuel and starter controls, Ralph started the pre-flight checks and prepared to start the engines. He would be running this test without a battery cart, so he first switched the Battery switch up to the ON position and confirmed the Voltmeter was registering current.
Following the new procedures, Ralph’s first job was to test that the Low Fuel Level Warning lights were functioning by pressing directly on the lights themselves and forcing them deeper into their sockets. Both lights glowed amber, which meant the bulbs were good and the warnings working.
The next series of checks were unchanged from previous P-38 models, checking Oxygen pressure, moving the throttles ¾ of an inch open, setting propellers to INC. RPM, propeller constant speed switches to AUTO CONSTANT SPEED, propeller circuit breakers ON, and mixture was at IDLE CUTOFF for both engines. After that, Ralph checked that both oil radiator flap override switches were in AUTO, both coolant flap override switches were in AUTO, and both intercooler shutter override switches also in AUTO before switching on both generators and the inverter switch to his right.
Since he would be flying with external Drop Tanks today as part of the fuel system tests he also turned the Bomb selector switches (with also controlled the drop tanks) ON and made sure they were SAFE just in case he needed to jettison them on takeoff due to an emergency.
Ralph ensured the Ignition Master switch and both engine ignition switches were OFF then called out of the open canopy for the ground crew to turn over the propellers while he set about checking the new fuel system. He first moved the old manual tank selectors to the recommended RESERVE position and checked that the Booster Pump Speed Controls were both at NORMAL. He followed that with confirmation that the Fuel Selector Override switches were both in the down, OFF, position and then turned the electric fuel selector knob to the 9-o’clock OUTER-WING position and moved both Fuel/Dilution switches to ON.
His fuel pressure gauges jumped up to hover between 6 and 8 pounds per square inch pressure, perfect. A flick of his fingers moved the Speed Control switches to EMERGENCY and the fuel pressure jumped up even farther, to about 18 pounds per square inch. After returning the speed controls to NORMAL, Ralph pressed the Outer Wing Tank Low Level Check Button and was happy to see that neither low level warning lights lit up, indicating there was at least five minutes of fuel in the tanks.
He then repeated the fuel pressure tests for the MAIN, RESERVE, and EXTERNAL to confirm proper operation of each of the new individual booster pumps. Although there was no way to gauge the fuel level in the external tanks, the MAIN and RESERVE tanks each had their own fuel gauges so there was no need to test levels through a separate procedure as there was with the outer-wing tanks. He left the selector on RESERVE and made one final confirmation that the speed selectors were at NORMAL.
Once he received the OK from the ground crew, he flipped on the Ignition Master Switch. Now was when he would test the new starter system and confirm that it allows both engines to start simultaneously as intended. With his left hand ready on the mixture controls, Ralph reached his right hand past the yoke, turned both Engine Ignition Switches to BOTH to equally share the load between the magnetos, and pressed both Left and Right Starter switches until he felt a resistant stop, indicating they were in the center ENER (Energize/Prime) position.
A familiar electrical hum started from both sides and starting building into a whining crescendo. After a few seconds the crescendo peaked and Ralph forced the starter switches through the stop until they were fully forward. The electric whine dropped in pitch but with a series of short pops the propellers jerked around in a few partial revolutions before both engines sparked to life. Ralph pushed the mixtures to AUTO RICH and the comforting roar of the big V-12’s filled his ears.
He released the starter switches, letting them spring back to their resting places, and watched the oil pressure gauges to confirm both engines were fully smooth and operational. As he let the engines warm up he made a note of the ease and success of the new startup procedure. He also took the opportunity to test his radio and hydraulic systems.
Once the engines had warmed up sufficiently, he increased to 2300 RPM and tested the propeller controls—finding he had to fine tune the right propeller a little to synchronize it with the left. Then it was the standard magneto checks, generator tests, as well as testing the radiator flaps and intercooler shutters before throttling each engine up to take off levels briefly to confirm the turbos were working and to adjust the throttle lever friction.
He was ready for takeoff.
* * *
Ralph’s flight tests today, with the starter procedure out of the way, was entirely related to fuel management. He was to test each tank through the electric control, the manual control, and to test cross-feeding between sides for all tanks, including the outer wing tanks which were now fully integrated into the main fuel tank selector valve.
His first tests were simply to go through the four different tanks with both engines drawing from their own side. The procedures for normal operation were very easy. He simply needed to confirm the Fuel Selector Override switches were both in the down, OFF, position, then turn the single fuel tank selector dial. Doing so changes a series of actuators on both sides to open fuel flow for the the selected tank. So, with both overrides OFF, moving the one free-turning knob to RESERVE switches both engines to draw from their respective Reserve Tanks and an electrical contact automatically turns on the Reserve tank booster pumps.
The way the engineers explained it to Ralph was that when the overrides are in the OFF position they activate the electrical circuits for the electrical fuel management systems and close a master valve actuator off the manual valve output line. The master actuator is set up so that when there is a steady low current flowing into it the valve remains closed and when the current ceases the valve automatically opens. The individual tank valve actuators--which are on bypass lines around the manual valve--are the opposite, so that their natural state is to be fully closed but when a tank is selected the valves for that tank remain open as long as there is current into the actuator. Therefore, the tank selector dial has a total of six contactors for each position—two to maintain current to the valve of the selected tank on each side, two which open the current to the fuel booster pumps on the selected tanks, and two more which connect the selected tanks to the Low Level Warning Lights above the selector knob.
While this system means that there is a constant low electrical drain to keep the master valve closed and the selected tank valves open, it does ensure that in the event of electrical failure or even just failure of the electric fuel management system all tank valves on the bypass lines automatically close and the master opens allowing fuel to flow from the old manual valves to the pilot’s left. Likewise, moving the override switch for one side to ON interrupts the current for the entire circuit on that side which causes all associated valves to close and that side's master to open and fuel can then be managed by the manual valve.
For the flight the airplane had been only partially fueled so Ralph could test not only the fuel tank selection but also the low level warning. This system, which was just an expansion of that put in place for the outer wing tanks in previous models, was designed to automatically ignite the Low Level Warning lights for the selected tanks on each side when there was only 5-6 minutes of fuel remaining in the tank, based on normal consumption at Maximum Cruise, or about six gallons of usable fuel. The idea was to give an obvious and visible warning to the pilot that his selected tanks were about to run dry with enough time for him to switch to a tank with more fuel. The hope was that this would dramatically reduce the number accidents resulting from fuel starvation when a pilot failed to switch tanks.
Once the tests for normal operation were complete, Ralph start testing the ability properly draw fuel across the airplane by cross-feeding the fuel from a single tank on one side to the engine on the opposite. To do this, he first moved the tank selector dial to desired tank, then turned the manual valve for the engine which would cross-feed to the CROSS SUCTION position, then simply switch the Fuel Selector Override for the cross-feeding engine to ON.
Ralph moved the tank selector dial to EXTERNAL and with his left hand moved the right engine manual fuel valve to CROSS SUCTION. With that set, he just reached forward and moved the right side Fuel Selector Override switch up to ON. He flew in this condition for ten minutes to confirm the cross-feed was working properly, then turned fuel selector dial from EXTERNAL to OUTER WING. The change happened without difficulty and he was relieved to discover that both engines continued run without interruption.
He flew on the left outer wing tank for about 25 minutes before the left Low Level warning light started to glow a soft amber. Ralph then switched on to the MAIN tanks, with the right engine still in CROSS SUCTION. He made a note of when the warning light turning on—when he landed the test engineers would check the fuel remaining in the tanks and those tanks when he switched off when the light came on should each have around five gallons of fuel.
Ralph repeated this process, draining the left MAIN tank down, before he switched the right side Fuel Selector Override back down to OFF. He ran on both MAIN tanks until the left warning light once again started to glow, it being drained before the right because of running both engines off it for a while. When the waning light turned on, he turned left manual selector valve to CROSS SUCTION and flicked the left override ON. Immediately the warning lamp turned off as fuel began to flow to the left engine from the right MAIN tank for a moment before he turned the selector dial down to EXTERNAL.
The plane flew for a good 10 minutes on the right drop tank before Ralph once more made the switch to the OUTER WING. This time, the fuel flowed form the right wing to right engine and through the cross suction valve to the left. He flew like this for another 20 minutes before the right low level warning light began to glow and he was forced to make a switch to run both engines from the right MAIN.
Half an hour later the right low level warning once more turned on and Ralph knew the flight testing was done. He turned the selector RESERVE, flicked the left override OFF, and turned back toward Burbank.
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Later that day the engineers reported back the fuel levels remaining in each tank. Ralph had only run each drop tank for 10 minutes, they started with only 50 gallons each and after landing it was discovered that left tank had 31.4 gallons and the right 30.7 gallons which meant they each lost just under twenty gallons—exactly as expected for running both engines for ten minutes at 2300 RPM and 35 in/Hg. manifold pressure.
Both MAIN tanks and both OUTER WING tanks had been run down until the low level warning light came one and they were found to have (from left to right) 5.6, 5.2, 6.1, and 5.8 gallons. The RESERVE tanks were used to fly in and were not run dry but had 14.2 gallons in the left and 12.7 gallons in the right.
In the end, Ralph and the engineers all agreed that the test was a resounding success. If they could get the new switches and new fuel management system produced in bulk and be allowed permission to interject them into the production they could only hope these improvements could arrive to the front by mid-summer.
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