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Fighter pilot question



 
 
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  #1  
Old October 6th 04, 06:21 AM
Peter MacPherson
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Default Fighter pilot question

Maybe this is a stupid question, but here goes.... ; - )

Why is it that when fighter pilots roll in on a ground or air
target they always seem to roll into an inverted dive? Is this
just my imagination? What's the benefit of an inverted dive?

Thanks,
Pete


  #2  
Old October 6th 04, 07:42 AM
Peter Duniho
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"Peter MacPherson" wrote in message
newshL8d.420077$8_6.33940@attbi_s04...
Why is it that when fighter pilots roll in on a ground or air
target they always seem to roll into an inverted dive? Is this
just my imagination? What's the benefit of an inverted dive?


Real fighter pilots can give a better answer. But when I've done the "air
combat" entertainment flights, the instructors have always told me that
standard procedure is to get your target above your canopy, and then pull
"up" on the elevator.

Any target on the ground would thus wind up being approached with an
inverted dive. An airborne target would only be approached in an inverted
dive if below you.

I presume that the primary benefit is that it's easier to take positive G's
than negative G's, and the idea is to get the nose of the plane pointing at
the target ASAP. That means maximum G's, and you want to be in a position
to deal with them safely and relatively easily.

I imagine that it's not actually true that a fighter pilot *always* uses
this procedure. But it is common enough that as a "fighter pilot for a
day", I've been instructed to use the technique as standard procedure.

Pete


  #3  
Old October 6th 04, 11:44 AM
Daniel L. Lieberman
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I believe that if you posted this question in rec.aviation.aerobatics the
answer would be the difference between positive and negative Gs on the body.
(The body can stand more positive than negative as can many plane designs.)


  #4  
Old October 6th 04, 12:30 PM
Viperdoc
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As a flight surgeon in a fighter wing I had the opportunity to get around 75
hours in F-16's, and asked the same question. Both previous posts were
correct- most planes can take more positive G, and a half roll and pull is
much easier to tolerate than bunting over. (a 8-9 G sustained pull is hard
to take, but a sustained push would be much much worse) Besides,as I recall
a 16 is only rated to around minus 3 to 4 G and +9 (depends on load
calculated by the on board computer, which limits the amount of G the
airplane will take regardless of how hard you pull or push).

With a good pull or push the G it is possible to load the airplane at a rate
of around 5-6 per second, so a hard push is very uncomfortable.

Of course, most of the pilots are envious that I fly an Extra 300, which
rolls faster than a 16 and is rated for +/- 10 G!


  #5  
Old October 6th 04, 02:43 PM
Corky Scott
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On Wed, 06 Oct 2004 05:21:39 GMT, "Peter MacPherson"
wrote:

Maybe this is a stupid question, but here goes.... ; - )

Why is it that when fighter pilots roll in on a ground or air
target they always seem to roll into an inverted dive? Is this
just my imagination? What's the benefit of an inverted dive?


They don't always (roll inverted to dive on a target), but in addition
to the already mentioned point of positive G's being easier on the
body than negative, there's also to consideration of keeping the
target in view. When you roll inverted you can look directly at the
target from that vantage point and not have your vision blocked by
fuselage and wings, and pull the stick back to bring the nose down
towards the target.

Times and aircraft performance have changed enormously since the days
of WWII. The Navy dive bombers approached their targets in at a
cruise setting (max cruise was 185 but they usually flew more slowly
than that to conserve fuel) and had to align as necessary depending on
the target, whether it was maneuvering or whether there were ground
obstructions to consider. Wind direction and strength were also a
consideration. Once the proper approach was decided, the flight
leader brought his squadron to the pushover point, snapped out the
dive brakes and then banked up vertically in the direction of the
target. The rest followed one after the other, peeling off
dramatically (for the camera), but they did not normally roll
inverted, they just let the nose slide down into their normal dive
angle. Since there was some matter of seconds passing between the
first to head down and the last, each dive varied some in it's descent
angle, although probably not by much.

If the target was a ship and was aware of the approach, it maneuvered
wildly for it's life. Destroyers were notoriously difficult to hit as
they were extremely maneuverable and narrow. The dive bombers
maneuvered during their dive to keep the target in sight. So poor was
the Navy's record in actually hitting a destroyer with a dive bomber
attack that it was only until the middle of the battle for Guadalcanal
that one was actually struck (by a dive bomber), finally. That it was
hit surprised the Japanese admiral who was on board. It wouldn't be
the last time the American forces surprised the Japanese at
Guadalcanal.

The German Stuka dive bomber actually had a target viewing window in
it's belly and the bomber nosed over once the target was in sight in
this window. The Stuka was also equipped with an automatic pull out
device that was adjustable for when it began pulling back on the
stick.

But the Stuka pilots also sometimes rolled inverted into their dives.

Fighter pilots during WWII often rolled in on their targets whether
they be aerial or ground, but not always. It depended on the
circumstances and where the target was sighted in relation to the
direction of flight.

By the time the experienced pilot got into combat, he was, or should
have been, familiar enough with his airplane that rolling one way or
the other while staying coordinated was second nature. Some German
pilots were so skilled that they could and did fire on approaching
bombers while rolling continuously. Not sure why this would be
necessary, but in some cases they fired and rolled so that they could
be on their back when they were close to the target so that they could
pull the stick in and dive out of the way.

The Germans discovered during the Battle of Britain, that their
Messerschmitt Bf109E's had a tactical advantage over both the
Spitfire's and Hurricane's they encountered. The Messerschmitt had a
fuel injected engine which was unaffected by negative G's while both
the British fighters used a carburator that cut out when subjected to
negative G's.

They learned that this difference gave them a crucial edge which
allowed them to escape if surprised from behind. They simply pushed
the nose over steeply (the British called this a "bunt") and shoved
everything to the wall while diving away. The Bf109 accelerated a
little faster than either of the British fighters in a dive but the
since the Spitfire and Hurricane's engines cut out in a negative G
situation, they were left behind. Well, left behind enough that most
of the time the Messerschmitt escaped.

The British countered by half rolling to follow. But this still cost
them vital time.

The Navy taught it's fighter pilots several attacks, one of which was
the direct overhead attack. In this maneuver, the airplanes
approached from opposite direction, the Navy fighter above by several
thousand feet. When the enemy aircraft disappeared from view under
the nose, the pilot was to roll inverted to keep the airplane in view.
At the proper moment, the stick was pulled back and the fighter dove
our of inverted horizontal flight onto the target.

I might add that often our only reference to fighter maneuvers is from
movies. Hollywood has long sacrificed historical accuracy for drama.
They've often considered rolling inverted to dive a very dramatic
shot, so that's what gets on film regardless the actual tactics.

Corky Scott
  #6  
Old October 6th 04, 04:08 PM
Jay Honeck
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Of course, most of the pilots are envious that I fly an Extra 300, which
rolls faster than a 16 and is rated for +/- 10 G!


I'm STILL telling people how I saw you SIT on the elevator without damaging
the plane.

That's an amazing aircraft you've got there, Doc.
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"


  #7  
Old October 6th 04, 04:56 PM
Robert M. Gary
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"Peter MacPherson" wrote in message news:DhL8d.420077$8_6.33940@attbi_s04...
Maybe this is a stupid question, but here goes.... ; - )

Why is it that when fighter pilots roll in on a ground or air
target they always seem to roll into an inverted dive? Is this
just my imagination? What's the benefit of an inverted dive?


Because they get air sick if they push the nose over . There are a
lot of G's at that speed associated with getting the nose down, the
G's feel better pushing you into the seat rather than up out of the
seat.

-Robert
  #8  
Old October 6th 04, 04:56 PM
Casey Wilson
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"Peter MacPherson" wrote in message
newshL8d.420077$8_6.33940@attbi_s04...
Maybe this is a stupid question, but here goes.... ; - )

Why is it that when fighter pilots roll in on a ground or air
target they always seem to roll into an inverted dive? Is this
just my imagination? What's the benefit of an inverted dive?

Pushing the stick forward to initiate the dive on a target results
in negative Gs. Rolling inverted and 'pulling' onto the target makes
positive Gs.
Early on in test and evaluation phases, prototype weapons (missiles,
bombs, etc.) haven't been subjected to all the stress tests to determine
their envelope. So, during early T&E it is safer to keep +1G on the weapons
platform.


  #9  
Old October 7th 04, 05:30 AM
Big John
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Peter

First, got lots of hours dive/glide bombing.

P/F-51
F-80
F-2H3
B-26K
Target marking with WP rockets in the 0-1/02.

These all were what we called glide bombers. Dive angle varied between
45 and 60 degrees. Power was reduced to 20" or 80% or so entering
dive.

Entry was in a fairly tight turn (depending on air speed and stall
speed) letting the nose drop below the target (keeping it in sight at
all times). As you rolled out you brought the nose up (+ G's) on to
target.

Prior to attack you set 'depression' in sight and all you had to do
was use coordinated maneuvers to get pipper on target and hold there.
Skidding etc to hold pipper on target would assure a miss.

Drop altitude depended on the size bombs you were carrying. The bigger
the bomb the higher the minimum altitude (or you blew yourself out of
the sky with your own ordnance). Saw several birds come home with
holes in the belly from dropping too low.

Saw a F-100 in VN push the envelope and knocked his hydraulics out.
Got nose up before controls locked and as bird stalled he punched out.

Bombing was hard work with the G's you pulled and formation to and
from target not to mention the anti aircraft fire.

All the birds in VN were glide bombers (A-1, AT-37, F-4, F100, F-5,
etc.)

Now to answer your question. It looks better on film if you roll over
and split 'S' . The movie I was in we did things that we would never
have done in real life (or combat). Sure looked good in the movie
thought )

Miss being 'point of the sword'.

Big John
`````````````````````````````````````````````````` ````````````````````````

On Wed, 06 Oct 2004 05:21:39 GMT, "Peter MacPherson"
wrote:

Maybe this is a stupid question, but here goes.... ; - )

Why is it that when fighter pilots roll in on a ground or air
target they always seem to roll into an inverted dive? Is this
just my imagination? What's the benefit of an inverted dive?

Thanks,
Pete


  #10  
Old October 7th 04, 11:17 PM
ffdds
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Nobody has yet mentioned that jet intakes run into problems feeding the
engine properly at negative angles of attack.

So the reasons are...

1) aerodynamic (inlet at negative aoa)
2) flight dynamic (can generate positive pitch rates greater than negative)
3) structural (can pull more positive g's than negative)
4) aeromedical (pilots can handle positive g's better than negative g's
5) situational awareness (during positive pitch rates can see "what is
coming" by looking up through the canopy)

I leave it to wiser minds to organize these into a hierarchy of importance.



 




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