Pelican's Perch #72:
The Legendary Zero (Part 2)
In this continuation of his checkout in a Japanese Zero, John Deakin does his preflight in the cockpit, fires it up and takes to the air in one of the very few flying examples of this famous WWII fighter.
Editor's Note: This is the second of a two-part series on flying the Zero. Read Part One first.Revisiting the very interesting aileron tabs, I have updated information. Thanks again to historian Alan Gaynor, who dug up further details on those strange devices. I got it almost right last month, but some documents he found state very firmly that the design intent was to make them servo tabs when the flaps are up, and to neutralize them completely when the flaps are down.
|(click photos for larger versions)|
|Flap Aileron Tab Mechanism|
I'm puzzled at all that; I would think that like any other airplane, as the airspeed drops, the roll control becomes naturally more sluggish. But control force does become lighter, and perhaps that's what they were worried about when coming aboard a carrier.
Now, back to the Zero's other systems.
The landing gear and flaps are hydraulically operated, and the gear will free fall to the down-and-locked position. Nothing strange there, but the hydraulic pump is electrically driven, "momentary only," and is turned on by a pushbutton on top of the control stick. The first time someone told me what that little black button was for, I flashed back on an old comedy routine. Something like, "So I went to pick up my girl at her house. I could smell her mother cooking in the kitchen, and her father answered the door in his underwear. I thought that was a strange place for a door."
In other words, it's a strange place for a switch.
Anyway, the drill is to select the gear (or flaps) up or down, then hold the button to turn the pump on. For "Gear Down," it's not necessary, as the gear falls and locks down just about as quickly with no hydraulics at all. A quick blip on the button feels good, though.
There's a big 24-volt battery behind the pilot's seat (accessible only by removing the seat), with an external power socket on the left side. It is fed by the engine-driven generator in the usual fashion.
As some of you know, I like to do a left-to-right "flow" in all cockpits, and this one is no exception. Most if not all of this can and should be done before entering the cockpit as many of the items cannot be seen when seated, even by the most agile pilot. For those of us who resemble a cork in a bottle, it's even worse. The object of the exercise is first to review what each control is, what it does, what to do if it doesn't do what it's supposed to, and second, set it for takeoff or engine start, if possible.
|Rear Fuselage Behind Pilot's Seat|
|Mystery Circuit Breakers|
The Hobbs is not original equipment, of course, and hardly worth noting here, but it is well to check the reading before and after flight for the records. One of four quick-disconnect seat attach points is visible, and these provide the only access to the battery. Note again the very simple, very clean construction, with no frills.
The mystery circuit breaker panel is behind and below the pilot's left elbow, another hard to reach place. Once buckled in, it cannot be seen, you just have to know it's there, and work by feel. Perhaps that's why they aren't marked. All should be in for flight, of course.
The upper circuit breaker is for the "modern" radios, as mentioned above. I usually leave that one out for start.
The middle one is for a fan up front, somewhere behind the instrument panel. There is nothing that I know of up there that needs a fan, but what do I know. Like most fighters, there's only a thin firewall separating a lot of horsepower from the cockpit, and cockpit temperatures often rise to 160º F or more, so the fan may be a good idea for the King radios. It has the sound of a fairly heavy electrical draw.
The lower circuit breaker is for the transponder.
The other lever is unmarked, but may be the drop tank release. The inoperative fuel valves may also be related to the drop tanks (not installed, not available). The fuel selector is shown in the OFF position, and must be ON for start, of course.
The nicely finished wooden trim wheel is a classy touch, but a contrast to the otherwise "utilitarian" cockpit. Trim should be set to about zero for takeoff. This picture also shows the double battery switches, and the friction knob for the throttle, prop and mixture controls. This is a very important item to check before takeoff, for if it's not set very hard, the throttle will, of its own accord, slide right back to idle immediately. If that happens, you can't let go of the throttle with your left hand long enough to tighten the friction, and you can't let go of the stick with your right hand long enough to do it, either. Guess how I found this out on my first takeoff? And no, I didn't forget it, it just takes more than I thought it might.
|Main Fuel Gauges and Electrical Panel|
Fuel gauges (in liters) should correspond to the fuel known to be in the tanks, and it's very, very rare for us to take off with less than full fuel in all tanks. All these airplanes are very short-legged -- no one wants to run out of fuel, and if there's a problem in flight, we do not want to be sweating fuel as an additional problem. It's unusual for a fighter to have more than two total hours of fuel, and one -- the little Polykarpov -- has only about 40 minutes to dry tanks.
At this time I switch on the gear lights and engine gauges for the start. The amber light for the tailwheel is usually on, but a quick touch of the stick-mounted hydraulic pump switch will cause a slight lurch, and the amber light is replaced by the green, for a few moments. We are told it's safe -- just a slight misrigging that we'll get fixed.
In order, left to right in the picture:
"Bat" for battery, of course. But apparently it doesn't switch absolutely everything off, there is some sort of unknown electrical drain that remains. The restoration team would find the battery dead in a day or three. They finally gave up and installed a "master master," the red guarded switch at the extreme lower left corner of the picture.
"Gen" for "generator. Nothing unusual here. It cuts in at about 1200 RPM, and there is a red warning light on the panel when it doesn't produce.
"Formation Lights." This switch controls a series of external lights on the wings and fuselage to facilitate night formation flight. Most military aircraft have these. They look like embedded nav lights, but are placed in several positions all over the aircraft, to give some depth perception in the inky blackness. (Night and instrument formation is not for the faint of heart!)
"Running Lights." Conventional nav lights on the wing and tail tips.
"Radio." Presumably a master radio switch. This switch is inoperative in this airplane, at least for the "modern" radios. It may control the ancient Russian radio gear, still installed for show. The real radio master switch is one of three unmarked circuit breakers below and behind the pilot's left elbow.
"Gear Ind." for turning on the gear indicator lights. I've not seen this before, but it's not a bad idea. Other airplanes have circuitry that will dim the gear lights (and other warning lights) by various means, either a dimming switch, or tied in with the nav lights. That can create problems when the lights are accidentally dimmed in the daytime. In the Zero, you'd get used to directly controlling the gear lights with the switch, and perhaps that would be simpler. There are nine individual gear lights in all, three for each leg, red for up, amber for in-transit, and green for down.
"Pilot Heat." Yes, that's what the placard says, but I think it's supposed to say "Pitot Heat." I haven't checked that out yet, but I will.
"Engine Gauges." This one is for all the engine instruments that require electrical power to operate. This one really amused me -- why on earth would I ever want to turn off power to the oil temperature gauge, or the ammeter, or the oil and fuel pressure instruments? I suppose the design intent was to furnish the pilot with a quick and dirty means of isolating each of the components of the electrical system, and there's a lot to be said for that. With a generator failure, this allows the pilot to select only what he wants, turn the battery on momentarily, then kill the power again. Or, with an electrical fire, to kill only the system causing the problem.
"Turn Bank." Power switch for the electric turn and bank indicator.
"Pilot Ind." I think this one identifies the red light above it as an indicator that the pitot heat is on.
The first switch on the bottom row is a mystery switch.
The second is the fuel boost pump, used for starting, takeoff, and landing, in case the engine-driven fuel pump fails. Like almost all airplanes that use gasoline, it may also be needed to reduce the formation of vapor bubbles in the fuel lines as warm fuel is transported aloft to lower pressures. Engine-driven fuel pumps generally don't pump bubbles very well, and electric boost pumps do.
The square panel is a raised cover that blocks access to a few more "mystery thingies."
The three red knobs are lighting controls, and the four red things at the forward end of the panel are the old-style fuse-holders.
Speaking of machine guns, they are right there. Right in the cockpit, high on the main panel, one on each side, cocking levers within easy reach, with the barrels firing out through the top of the cowling. The noise must be incredible. Fortunately for the local FAA, the guns are permanently disabled.
|Forward Left Panel|
Next to the EGT is the clock, of course, then the airspeed indicator. It seems odd to have "1.5" show 150 knots, but the airplane has so much "feel," it's not even necessary to have this instrument, except for the airspeed limitations. The red "Gen Off" can be seen just above and to the right of the airspeed.
The mag switch is worthy of note, and I think I'm glad the restoration team went to the effort to label the positions! It is, of course, exactly backwards from the usual mag switch. One has visions of cranking the engine endlessly, burning up starter after starter, trying to get it going with the mags off.
At the very bottom center is the primer switch, a momentary "push to prime." It simply operates a solenoid, which opens a valve, allowing electric fuel pump pressure to shoot fuel into the gear-driven supercharger impeller.
|Forward Right Panel|
At the extreme right side of the picture is the handle for the emergency hydraulic hand pump. It is stowed in a pair of clips there. I prefer to just install it for all flights -- it's not in the way, and that's one less thing to fumble when needed.
|Hydraulic Reservoir and Rudder Pedals|
The glass in the hydraulic reservoir has darkened with age, showing black here, but it's reasonably readable in daylight.
|Oil Shutter Control|
|Cockpit Air and Uplock Release|
|Cockpit Right Side|
If the gear handle doesn't unlock the up latches, there are two additional handles, one for each main, with very short cables directly to the up latches.
Just to the right of the oil cooler shutter control, there is an almost identical control for the cowl flaps. These must be wide open on the ground at all times, or the CHTs will rise very rapidly. They are half-closed just at the start of the takeoff through the climb, and may be closed for cruise.
The "Morse Key" had me puzzled for some time, until I finally fondled it. It has the classic feel of the telegraphy button of yesteryear, but it is much larger. I don't know if it works; I'll try a little Morse on the Camarillo tower, next time.
In this picture, I've installed the handle for the hydraulic pump, where I prefer it for all flights. I'd hate to need it in a hurry, grab for it in the stowage slot, drop it, then have to fumble around under the seat.
The seat adjustment is odd. It is mostly for up and down, and the up position is very useful for taxiing, as the view forward is blocked by the nose. It's still necessary to S-turn constantly to see ahead. As the lever is moved downward, the seat portion moves a bit forward first, then down, then back sharply, but the backrest hardly moves fore and aft at all. It is very uncomfortable in any position, and not just because of my size. It must have been torture on a long mission, even for a very small person.
Not shown here are the shoulder straps, which I consider unsafe and unusable. First, it's not possible to reach all the controls with them on, and second, they do not come off the shoulders horizontally, to keep the upper body from folding forward. They drop almost vertically behind the pilot, and in an accident, they'd compress the spine badly, without doing anything good. I choose to fly without them. I also find that I cannot wear my normal helmet, the canopy is too tight, and my head is already jammed up into the top, where it's low and narrow (the canopy, not my head).
The "Safety Latch" is a spring-loaded pin that blocks the gear handle from being pulled into the UP position. It is retracted by the right main gear oleo extending to full travel, which pulls on a cable. The pin can also be pushed out of the way, if needed. When the handle goes past that pin, and fully into the UP position, it depresses the sensor, and lights the red UP lights.
The hydraulic pressure gauge (Kg/sq/cm) is also located where only an owl could look at it.
Fire It Up
Having completed a thorough external preflight, making sure there is fuel, oil, and hydraulic fluid, and having set up the cockpit, it's time to start. We have to "call mother," which means to notify CAF HQ that we're about to commit an act of folly ... er, flight ... with one of their precious aircraft. A fire guard must be posted, the external power plugged in, and the moment of truth arrives.
Now, I'm not religious, but I must confess, at that point, I always quietly and very sincerely say to myself, "Please God, don't let me screw this up." These are historically priceless airplanes -- irreplaceable -- and I cannot imagine the burden of knowing I was responsible for the loss of one. Full insurance is impossible to get, and the CAF has the best around, covering up to $600,000, with a $50,000 deductible. Pilots are required to carry an additional policy costing $495/year, which covers $40,000 of that. Pilots are on the hook for the remaining $10,000. That's a small fraction of the real value, probably north of two million.
One of the jokes is, "Don't bother to bail out -- we'll kill you if you survive."
The wise pilot will close the canopy for the start, for two reasons. First, when a radial starts, it flings oil everywhere, including into an open cockpit, and onto the teeth and glasses of the pilot. Second, if there is a starting fire, the closed canopy will provide a lot of protection -- and prevent singed eyebrows, and worse.
Mags off (Yes, OFF), fuel pump on, get the high sign from the fire guard, and hit the starter switch with the right hand. Nothing happens. Hmmm. With a little more fondling, I found that if I hold my mouth just right, and move the starter switch just so, and wait patiently for about five seconds, the engine does turn. I think we'll need a new switch, eventually.
Ooops, the prop stops, hard, with the starter still trying. That's the sure sign of a "hydraulic lock," where some oil has become trapped in a lower cylinder, and the piston cannot get to top dead center. Power off, unbuckle, go find the tools, and pull the bottom three front plugs, looking for oil. None found. Pull the next plug on either side, and we get a gusher from one of them. Put everything back together, buckle up, and we're ready to go, again. The sun is hot, the airplane is hot, and my Nomex flight suit is hot, so I down some of that clear liquid that comes in plastic bottles at $6 per gallon. (Don't complain to me about high fuel prices, when water is three times as much!)
Seriously, one of the deadly traps in flying these old beasts is dehydration. Pilots must make an effort to drink lots of fluid. The heat in these cockpits is incredible.
This time, the engine turns well, and at 12 blades, I switch on the mags (backwards, remember), and start priming. The big radial coughs to life on prime alone, and my right hand comes quickly off the starter to the throttle (cross-cockpit), making small adjustments to get the engine running smoothly at about 900 RPM. I continue to hold the primer button down continuously with my left hand while checking the oil pressure. After some time running on prime alone, I push the mixture forward with my right hand, continue to hold the prime until the engine floods from too much fuel, then I let go of the prime. The engine catches for a second, and quits, now not enough fuel to run! I prime some more, in bursts, supplying enough extra fuel to keep it running until all the air gets through the carburetor, and all the seals and diaphragms get wet and start doing their thing. Slowly, the engine needs less and less prime, and finally it will run smoothly on the carburetor. Boost off, to check the engine-driven fuel pump. Push in the circuit breaker for the radios. Put the flap lever down, hit the hydraulic switch, and confirm they work, then pull them back up. Give the ground crew the signal to pull the external power cart, and we're on our own.
With all radials, the rule is to not exceed 1,000 RPM until the oil temperature has come up to at least 40º C, but with the Zero, it takes only about 1,000 to start moving, and about 700 to 800 to keep moving, so there's no delay waiting for the oil temperature to come up. A quick ATIS check, a call to Ground Control, and we're off.
Except for not being able to see straight forward, the Zero taxis very nicely. The rudder has some effect in the prop blast, an occasional touch on one brake or the other herds things along, and we S-turn off the ramp, all the way to the runup pad.
Runup is quite conventional: Check temps and pressures, increase power to about 1600 RPM, and cycle the prop a couple times to circulate warm oil into the prop dome and governor and check function. I generally do a short mag check at this point, as a preliminary check, so that the high-power mag check is less likely to cause snarfing and barfing if there is a malfunction. On most radials, we would next run the engine up to "Field Barometric Pressure," that reading found on the manifold pressure gauge before starting (about 29" at sea level, 25" at Denver, etc.). The engine should produce some specified RPM at that setting, regardless of field elevation. However, the Zero (and the Hurricane, and the Spitfire) is very light in the tail, and if that kind of power is pulled, the airplane will either nose over and get a prop strike, or the brakes simply won't hold it. Throttle at 25" is enough to get about 2,000 RPM, and that will have to do. I check the mags again, at that setting, and they each drop about 100, which is fine.
Flight of the Zero
Runup complete, I run my mental litany, "Controls, Instruments, Gas, Flaps, Trim, Prop, Runup," and there is suddenly nothing to prevent flight but a call to the tower. I think I said something like, "Tower, Experimental Zero, my first flight in this airplane, and the first flight for the airplane since restoration (a small lie), so please let me know if you see anything abnormal? We're ready for takeoff, would like a left turn around the airport, climbing overhead."
"Roger, Experimental Zero, cleared for takeoff, good luck!"
While taxiing onto the runway, I do the final items, canopy closed and locked, fuel boost on, cowl flaps cranked closed halfway, and last, tailwheel locked when aligned. Power up to about 25" for a final check, brake release, and bring the power in gently. The very light airplane leaps forward, and is literally off the ground in about 500 feet, still in the three-point attitude, and before I can get the full 50" of MP. This is very common on most "first flights," for I'm not willing to bring the power up "briskly" until I've had a few takeoffs, and have a feel for the airplane.
Many talk about the "torque," and "p-factor," but unless I am deliberately thinking about it, I never notice it on any airplane, unless I happen to run out of rudder. Even then, it's instinct to just back off a little power to maintain control. For that matter, my Bonanza takes absolutely full right rudder if I haul it off the ground at minimum speed, as bad as any fighter!
We lift the fighters off in near-three-point attitudes because most of them have very large props, and it's very easy to ding one with the tail high. We also strive for three-point landings, for the same reason, and we never try to "pin" one after a bounce. That's a lousy technique in any airplane, worse in the fighters.
Once off and climbing steeply at about 40" of MP, I took my hand off the throttle to retract the gear, and the manifold pressure instantly started dropping, big-time. Ahh, rats -- shades of my first flight in the Bearcat -- the throttle friction wasn't tight enough! Not a problem, just push the throttle back up, haul the nose up to keep under gear speed, turn left around the airport, climbing, then just let the power come back while pulling the gear up, trimming, and tightening up the friction lock as hard as I can.
No danger, it just looks amateurish, like I forgot the gear. I hate that. I noticed right away that I had to hold a lot of left aileron for level flight, but since I had expected that, it was no surprise.
I climbed to about 8,000' at 150 knots, turning, pitching, playing with the airplane. It very quickly became obvious that the roll rate was very impressive, and it was fun going to full lateral stick deflection, rolling from a 90-degree bank one way, to 90 degrees the other, and back, but without loading it up. The roll response is just delightful. As I gained altitude, I started pulling more and more in the turns, loading things up, but not over about 2 to 2.5g for this first flight. I kept trying that at slower and slower airspeeds, until the airplane started talking to me, saying, "Go ahead, just a little more, and I'll show you something." Again, not for a first flight.
At 8,000' or so, I turned off the boost pump, closed the cowl flaps, and started playing. I did a couple 1g rolls, just because it would have been a sin not to, then played around with the gear and flaps. As expected, the heavy aileron requirement reversed almost instantly as the flaps extended, and back again as they retracted. I was rather pleased with myself for catching that before the flight, as it would have been a rude shock with no warning.
I did a couple of level approaches to stalls, light power and no power, but again only the point where the airplane started talking to me. I just wasn't interested in getting aggressive until the control problems were fixed. With full flaps, I was able to maintain well under 50 knots indicated, but who knows how accurate that is. We'll need to do a little formation work with a slow airplane to find that out.
The airplane needs trim tabs for all three axes -- pitch trim alone isn't enough. Any change in speed causes changes in all three axes, which is not uncommon to fighters; some are just better than others.
Clear of the runway, crank the cowl flaps open, boost off, flaps up, push the hydraulic button, and let out that deep breath I took back when I hit the starter switch.
Once More Around
It's another type of sin to do something this much fun only once, so I taxied back to the active, and tried again. More confident in the airplane this time, I got the full 50" of manifold pressure before lifting off, held the attitude, pulled the gear up, accelerated to 140, and then pulled the nose up and left, to the downwind. Much more satisfying!
On the third flight, I actually had time to get the power up, and enjoy the takeoff roll for a few seconds. Funny how a first takeoff goes by in a blur, and then they slow down with practice.
I taxied home to the CAF ramp, happy, and wringing wet. Sweaty business, flying old airplanes.
Whenever I complete one of these flights, I try to act nonchalant about it, but I guess my face gives me away. "Aw, just another airplane." "Riiiiight."
I didn't get another chance to work on or fly the airplane for several weeks -- too much "other stuff" going on. Alan Gaynor pitched in again, and adjusted the linkages so they more closely resemble the descriptions from so long ago. He was ably assisted by David Baker, a newer member, who also happens to be my chief pilot on the Gulfstream in my other life! Aviation is such a small world. I had to go work, and I'm touched that these two would donate their time and effort to do this work.
As it happened, I was available to do a test hop the day they finished up the adjustments (funny how I can get there to fly, but not to work!) Just after pulling the gear up, I got to enjoy my fifth electrical smoke and fire drill, as electrical smoke filled the cockpit, and very heavy smoke poured out from behind the electrical panel by my left knee. I got one quick emergency call off, then shut down the electrical system, flew a tight pattern, and landed without flaps, getting a green light from the tower. By the time I was on base leg, the fire was out, and the smoke was gone. We have not yet removed the panel to see what was burning, but I'll bet it will be very obvious.
The Hobbs meter didn't even roll over a tenth, so I guess I'll just do "0.1" -- it's a flight worth logging. Alan and David were there to meet me with hopeful faces when I shut down, and someone else asked, "What's wrong?" I told them, but all Alan and David said was, "Never mind the electrical smoke, how'd it fly? Did the tab adjustment work?" Boy, talk about concentration! All I could say was, "Well, I don't remember having to hold so much left aileron, but things were happening kinda fast, so I'm not sure." I guess once the power was off and the sparks stopped, I should have just gone on with the tests without electrics and radios. Decisions, decisions, decisions. I elected to get it on the ground. Besides, the Hurricane was waiting for me, and I didn't want to miss that. It was a really good day for me: I got to fly my Bonanza to Long Beach, fly a Gulfstream to Santa Ana, Bonanza back to Camarillo, then the Zero, and finally the Hurricane. I am truly fortunate.
Now, do I do a column next month on the Hurricane, finish up the G-IV, or continue with the Air America stories? Decisions, decisions, decisions.
Be careful up there!