Stupid Aviation Questions...Please Help...

[muckmaw]

Here's the deal. I volunteer at an aviation museum and I'm whats called a Costumed Interpreter...meaning, I wear all the flight gear and walk around talking about the planes, etc.

Now, I was never given any training, so I rely on my own studies to gather info, but there are some things I just cannot find.

Any chance of getting some help on these questions?


1. Are fighter cockpits pressurized? If so, why do pilots wear oxygen masks. If not, why the oxygen mask below 10k?

2. Whats the difference between the Air National Guard, and the Air Force and Air Force Reserve.

3. How many Gs do you pull when you eject?

4. How long does it take to learn to fly for the military?

5. Why does one book say the A-10's rate of fire on the GAU-8a is 4200 RPS, and another says 2000 RPS. Is it adjustable?

Thanks in advance.

[CyranoAH]

I believe I can help with the first question.

Modern Combat Airplanes do have pressurized cockpits, but just to a certain altitude pressure. You have to understand that the greater the difference between the external and internal pressure, the more the structure has to withstand... if the cockpit pressure was to be set to sea level pressure, the canopy would eventually break due to excessive tension.

So why pressurize it at all? Well, while the pilot cannot breath the lo-press oxygen at 33.000 feet, the body does appreciate the higher pressure.

As for the oxygen masks, pilots must breath oxygen for some 30 to 45 minutes before going to high altitudes in order to break any nitrogen bubbles that we all have, and that would cause severe problems if they were to grow in size due to reduced pressure.

I'm sure eagl will answer this question (and of course the rest) much better than me, but let this serve you as an introduction

Daniel

[Curval]

Originally posted by CyranoAH
As for the oxygen masks, pilots must breath oxygen for some 30 to 45 minutes before going to high altitudes in order to break any nitrogen bubbles that we all have, and that would cause severe problems if they were to grow in size due to reduced pressure.Daniel

This is interesting...classic "bends" prevention, which makes sense, I guess.  

What is considered "high altitudes"?  

If this is the case then you couldn't scramble fighters to intercept really high bogies if they are within a calculated distance from the base, right?  The pilot would get seriously "bent" if he went up too fast?

[-tronski-]

Originally posted by CyranoAH
I believe I can help with the first question.

Modern Combat Airplanes do have pressurized cockpits, but just to a certain altitude pressure. You have to understand that the greater the difference between the external and internal pressure, the more the structure has to withstand... if the cockpit pressure was to be set to sea level pressure, the canopy would eventually break due to excessive tension.

So why pressurize it at all? Well, while the pilot cannot breath the lo-press oxygen at 33.000 feet, the body does appreciate the higher pressure.

As for the oxygen masks, pilots must breath oxygen for some 30 to 45 minutes before going to high altitudes in order to break any nitrogen bubbles that we all have, and that would cause severe problems if they were to grow in size due to reduced pressure.

I'm sure eagl will answer this question (and of course the rest) much better than me, but let this serve you as an introduction

Daniel

Well you learn something new everyday. I'd always thought the O2 mask was for helping combat G forces etc. or something along those lines.

 Tronsky

[mietla]

Originally posted by muckmaw
5. Why does one book say the A-10's rate of fire on the GAU-8a is 4200 RPS, and another says 2000 RPS. Is it adjustable?

 

switch

[AKS\/\/ulfe]

Curval, the space shuttle goes from 0ft sea level to outer space in like 10 minutes.. I'd guess it wouldn't be much dif than a jet scrambling against intruders.

(dunno, just offering an observation)
-SW

[Hortlund]

Originally posted by AKS\/\/ulfe
Curval, the space shuttle goes from 0ft sea level to outer space in like 10 minutes.. I'd guess it wouldn't be much dif than a jet scrambling against intruders.

(dunno, just offering an observation)
-SW

But surely the space shuttle is pressurized "at sea level"?

[AKS\/\/ulfe]

Hell if I know.
-SW

[Hortlund]

Well...thing is when you see those astronauts on tv doing their fancy floating around astronaut stuff, they never wear oxygen masks...hence my theory that the cabin is pressurised @ sea level.

[AKS\/\/ulfe]

Prolly right, I didn't really think that far ahead. On launch they are typically fully suited (helmet 'n all).
-SW

[gatso]

Most cockpits are pressurized to somewhere between 0.6 and 0.8 atmospheres. I guess military generally go lower than this.

Depends on the type of pressurization. You need to ensure an adequate supply of oxygen to the pilot, easiest way of doing this is to give it to him directly through a mask. Oxy systems into the cabin require more (heavy) eqiptment.

How may G's you pull on eject varies. Depend on the seat but can be anything from 20-30g ish over a small space of time. Generally the newer seats pull higher G but the way they are built means the pilot stands a much better chance of coming out of it with no injuries.

I'll have a look at my background docs from the RAF, I'll post on the 'how long does it take to qualify' thing tomorow if no one else does.

Gatso

[Kirin]

I guess astronauts are suited up on take-off in the case something goes wrong which could lead to immediate depressurization - what is all but healthy...

[Thorns]

Kirin's got it....There is not much volume inside a pressurized cockpit of a fighter.  Loss of pressurization at high altitude would render the pilot breathless(Payne Stewart Airplane).  The Military knows they aren't there for a picnic, so they are combat ready when the wheels leave the ground.

Thorns

[Zapata]

Originally posted by muckmaw
1. Are fighter cockpits pressurized? If so, why do pilots wear oxygen masks. If not, why the oxygen mask below 10k?

They're pressurized starting at 8k MSL to maintain a cabin pressure of 10k up to a certain altitude (about 25k I think, then it increases at a slower rate to avoid bursting the cockpit as mentioned earlier).  The regs say O2 isn't required below 18K, and I drop my mask as often as I can.  We refer to it as "the squid" cause it feels like one's stuck to your face ("It's sucking my will to live!").  A lot of guys will drop their masks below 18-10k, running the risks of facial injuries in an ejection, but after a couple of hours of smelling the chilli dog you had for lunch and having the skin rubbed off the bridge of your nose, it's nice to take a break.
In the event of a rapid decompression due to malfunction/battle damage a person's TUC or time of useful consciousness without an oxygen supply at high altitudes is reduced to seconds.  Basically you black out before you even know what happened due to the oxygen level of your blood dropping below the necessary level to stay awake.  It's been theorized that the crew of Payne Stewart's plane experienced a rapid decompression and couldn't get their emergency O2 masks on in time and passed out at high altitude.  The plane's windows were fogged up from the inside as reported by the F-15's scrambled to intercept it, a common feature of rapid d.  If the plane was on autopilot, it would take quite awhile for it to descend to thicker air, by which time unconsciousness would have led to death at the oxygen-scarce higher altitudes.  Tragic.
Additionally, in cases of high altitude ejection, the seat (I'm talking ACESII) will stay with you until lower altitudes allow a safer chute opening.  So while you're falling with your seat from 50K to around 20k your O2 mask alows you to breathe using the seat's emergency O2 bottle, without which you'd be unconscious from a lack of oxygen by the time your chute opened.
 
2. Whats the difference between the Air National Guard, and the Air Force and Air Force Reserve.

Insert punchline here.

3. How many Gs do you pull when you eject?

I think it's around 23 G's for an ACES II seat.

4. How long does it take to learn to fly for the military?

Typical fighter track:
Joe College gets 30-40 hours in light aircraft from the USAF, basically a free private pilot's license before going to UPT or undergraduate pilot training, which in the USAF takes 12 months.  He's then sent to IFF or introduction to fighter fundamentals where he begins his tactical training in AT-38's (T-38's with gunsights and bomb racks).  This is a 2 month course after which he's sent to an FTU or formal training unit which is teaches him to fly his particular fighter aircraft.  Some courses last 6 months (F-16) to nine months (F-15E).  By the time he gets to his fighter unit he's got about two years invested.  

5. Why does one book say the A-10's rate of fire on the GAU-8a is 4200 RPS, and another says 2000 RPS. Is it adjustable?

Our gun has a high and low rate of fire (F-15E) which we can select in the cockpit.  We've been running in it in low rate to prevent jams.  Can't speak to the Hog's cannon.  Some guys at work came from the A-10 though, I could ask them.

[muckmaw]

Thanks ZAP!

Thats some great info I can pass on to the tourists.