YFM-1 Airacuda

[nuuumannn]

Would there have been a problem with the guns firing through the propeller if the guns pointed forward?

Yes, the Daffy was not fitted with synchonisation gear, although there was a switch in the turret that the gunner flicked that enabled the pilot to fire the guns remotely when faced directly forward. The pilot had a firing button on his control column but did not have a gun sight. To avoid shooting off his propeller the guns had to be elevated to an angle of 19 degrees above the horizontal.

The concept of the Daffy was similar, but not the same as the Airacuda - it too was a bomber destroyer but it was to work in conjunction with single-seaters as a pure interceptor. The Daffys were to attack the bomber formations from the side and below to take advantage of their defensive weak points, which would cause the bomber formations to break up, after which the single-seaters were to take care of the stragglers.

 

[nuuumannn]

Most hydraulics are driven by pumps that are mechanically driven off the engine right?

Yes, but some aircraft also had electric motors that worked as backup pumps for hydraulics if the aircraft suffers engine failure. In some multi-engined aircraft, not every engine had a hydraulic pump, so backup systems were required. These days electrical systems work off multiple sources. Your average large aircraft has engine-driven (and APU-driven) AC and DC generators, inverters (for converting DC to AC), transformer rectifier units (TRUs, for converting AC to DC) and of course batteries.

In modern aircraft, APUs are gas turbines and are there to provide essential systems, such as air conditioning pumps, lighting and so forth required on the ground and many but not all aircraft equipped with one the APU won't work in flight.

 

[Shortround6]

How many rounds did the YFM-1 have in the 37mm cannon?

I believe they used 5 round boxes. ????

 

[XBe02Drvr]

With a relative few exceptions aircraft engines are not dependent on the electrical system.

But, however, when the fuel pumps are electrically rather than mechanically driven, the engines ARE dependent. Crazy way to design an airplane, to my way of thinking, but I'm not Larry Bell.

 

[XBe02Drvr]

So, the problem would have been not just hypothetical/theoretical but practical knowledge to make it work with both the particular gun and aircraft installation?

How often does theoretical knowledge turn into flawlessly working hardware without a passel of tweaking? Pretty damn rarely, as far as I can tell.

 

[ThomasP]

Per the manuals, the 37mm guns were clip fed. There were 22x 5-round clips per gun, so 110 rpg.

 

[Zipper730]

Regarding Boulton Paul Defiant

Angled 12 o'clock high. Sort of like Schrage Musik.

As I understand it, the rationale for the turret fighters were basically that it would have the benefit of upward tilted guns used in the Great War (so named because people largely did not expect a sequel that was bigger, longer, and uncut), with the ability to also vary the exact elevation, and also rotate them around.

Regarding the YFM-1's APU

" all electrical systems became inoperative: NO fuel pressure, NO vacuum, NO hydraulic pressure, NO gear, NO flaps and NO ENGINES."

I quoted that section because I was trying to point out the absurdity of calling it an "auxiliary" system when it affected almost everything the plane had that was essential.

. . . some aircraft also had electric motors that worked as backup pumps for hydraulics if the aircraft suffers engine failure.

So, I guess the electrical system runs off the battery in that case?

But, however, when the fuel pumps are electrically rather than mechanically driven, the engines ARE dependent. Crazy way to design an airplane, to my way of thinking, but I'm not Larry Bell.

It's pretty dumb as that sounds like you couldn't get the engine restarted if you couldn't get the fuel pumps working, and if the fuel pumps are driven by the engine, you are screeewwed...

Regarding the YFM-1's cannon

How often does theoretical knowledge turn into flawlessly working hardware without a passel of tweaking? Pretty damn rarely, as far as I can tell.

I would figure passel's of tweaking would almost be expected when translating theory into practice. The question is how big is that passel going to be?

Per the manuals, the 37mm guns were clip fed. There were 22x 5-round clips per gun, so 110 rpg.

That seems like that would be a pretty large belt. From what I remember the P-39's ammo capacity for the 37mm was around 30 rounds, and 58 for the P-63

 

[XBe02Drvr]

It's pretty dumb as that sounds like you couldn't get the engine restarted if you couldn't get the fuel pumps working, and if the fuel pumps are driven by the engine, you are screeewwed...

In a conventional setup you would have an engine driven fuel pump AND an electrical boost pump. Basic redundancy. However with only an engine driven pump an engine failure does NOT necessarily mean you are screwed, as inflight engine failures don't automatically result in the engine stopping rotation. It will windmill unless the prop is feathered. If the failure resulted from a fuel system valvology brain fart, fixing the issue will restore fuel flow and return power to the still windmilling engine. This happens more often than the uninformed would suspect.
Designing an all-electric airplane with ONE anemic generator, a small battery, and depending on a full time piston pounder APU is downright lunacy in my book. Gasoline powered reciprocating APUs haven't been historically real confidence inspiring performers. Nowhere near the reliability and ease of use of today's gas turbine versions.

 

[SaparotRob]

"Fuel system valvology brain fart"
If that doesn't deserve a bacon nothing does.

 

[XBe02Drvr]

"Fuel system valvology brain fart"
If that doesn't deserve a bacon nothing does.

Not in the house please! My cats'll be climbing the kitchen range. They KILL for bacon!

 

[SaparotRob]

Who wouldn't?

 

[MIflyer]

Read about a mishap on Youtube. It was a P-51 subscale replica powered by a automobile V-8 engine with a conventional automobile spark ignition system. For some reason the gear did not lock down - they did not seem to know why. But the electrically powered hydraulic power pack had been modified to not shut off until the limit switches tripped, rather than pressure switches as designed. With the gear not up the hydraulic pack ran until it blew the circuit breaker and that killed the engine ignition. Deadstick time, and with a gear that was not locked down....

 

[XBe02Drvr]

"Fuel system valvology brain fart"
If that doesn't deserve a bacon nothing does.

Two guys in a Twin Comanche died at my local airport from a "fuel system valvology brain fart" back in 1978. They were just descending out of the soup when I heard the engine speeds diverging as one died and the ice laden plane augered in. They hit the ground a split second before the ramp agents slammed shut the baggage door on a Twin Otter over at the airline ramp, and the two sounds were practically identical from where I stood. I still hear that sound in a dream from time to time.

 

[nuuumannn]

So, I guess the electrical system runs off the battery in that case?

Depends on the aircraft and the battery capacity. Big aircraft have multiple back-up systems, whereas most smaller aircraft had/have 12-volt batteries, which don't last very long if you run systems off them, hence AC and DC gennies. Smaller aircraft don't really need big capacity electrical systems so don't always need beefy AC power, a DC gennie or an alternator (which is AC current anyway) is enough, but in event of engine failure and your engine-driven electrical source failing, you're gonna head for the ground pretty quickly at any rate, so electrical systems might light your way to the crash site.

 

[XBe02Drvr]

Read about a mishap on Youtube. It was a P-51 subscale replica powered by a automobile V-8 engine with a conventional automobile spark ignition system. For some reason the gear did not lock down - they did not seem to know why. But the electrically powered hydraulic power pack had been modified to not shut off until the limit switches tripped, rather than pressure switches as designed. With the gear not up the hydraulic pack ran until it blew the circuit breaker and that killed the engine ignition. Deadstick time, and with a gear that was not locked down....

Ouch!! Why was engine ignition on the same circuit and with no backup system? Speaking of brain farts! Hello? Anybody home?

 

[XBe02Drvr]

Depends on the aircraft and the battery capacity. Big aircraft have multiple back-up systems, whereas most smaller aircraft had/have 12-volt batteries, which don't last very long if you run systems off them, hence AC and DC gennies. Smaller aircraft don't really need big capacity electrical systems so don't always need beefy AC power, a DC gennie or an alternator (which is AC current anyway) is enough, but in event of engine failure and your engine-driven electrical source failing, you're gonna head for the ground pretty quickly at any rate, so electrical systems might light your way to the crash site.

I haven't flown a plane with a DC generator since the T34 in the early 70s. They've all had automotive style aircraft alternators, even the oldie goldie ones that originally had generators. The worst was an early Cherokee 140 that had no generator/alternator warning system, just a poorly lit, minuscule ammeter in an awkward location at the bottom of the instrument panel. You had to tilt your head to the side and look beneath the control yoke to check it, which would raise havoc with your sense of orientation if in IMC or under the hood. Oddly enough, the CFIIs in the club seemed to prefer it for instrument lessons. I've had a prejudice against "Hershey bar" Cherokees ever since, although I have done instrument instruction in them when necessary.

 

[MIflyer]

My Ercoupe has a 12 amp generator, just like it came off the assembly line in Feb 1946. We are in the process of installing an alternator.

An advantage of a generator is that if the battery is dead and you prop the airplane to get it started, the generator will still supply power; an alternator would not do that.

 

[nuuumannn]

I've had a prejudice against "Hershey bar" Cherokees ever since, although I have done instrument instruction in them when necessary.

Never worked on bug smashers, so dunno what their electrical requirements are, alternators are probably the go these days I'd say. Same result though, batteries aren't very useful for much else once the engine stops.

 

[XBe02Drvr]

Same result though, batteries aren't very useful for much else once the engine stops.

Only in a twin with feathering props does a failed engine consistently stop turning. Fixed pitch and most constant speed props on singles will windmill when they quit unless the pilot goes to great lengths to stop them by hovering on the edge of a stall and waiting for it to wind down. Only worthwhile if you've got plenty of altitude and need to maximize your glide distance to the nth degree. Otherwise, your increased sink rate during your ultra slow flight to get your prop stopped will likely negate your improved L/D from eliminating the windmill.
One of the advantages of being young and foolish is the opportunity to go out and teach yourself a bunch of things the instructors don't, before you acquire the inhibitions that come with more experience. Having a fleet of different aircraft types in the club, and a number of small, remote, uncontrolled airstrips nearby, gave me opportunities to acquire a variety of experiences most low time private pilots don't get.

An advantage of a generator is that if the battery is dead and you prop the airplane to get it started, the generator will still supply power; an alternator would not do that.

If you've got a windmilling prop (or stupidly "split" the BAT/ALT rocker switch) and a dead battery and can access the main bus through a cigarette lighter or 12V power socket, you can "flash" the alternator windings from the cockpit if you have a small portable 12V battery(alarm system or motorcycle) and the appropriate plug. Once "bootstrapped" this way the alternator will keep generating as long as its rotor turns. I've spoken with long range ferry/delivery pilots who carry a rig like that with them on long flights.

 

[MIflyer]

The F-16 has a fly by wire flight control system, so if you lose the engine or just the IGD you are going to lose everything. So it has an Emergency Power Unit powered by hydrazine to enable them to get it on the ground before the pilot ends up being like a guy in lawn chair at 20,000 ft with only a Nintendo game for company.