[sci.military] Afterburners on military aircraft question.

bash@ihlpb.ATT.COM (Basham) (06/09/89)

From: bash@ihlpb.ATT.COM (Basham)

I've played a lot of flight simulators on my PC, I even worked on
military chopper simulators for a while.  Lately I've been playing
FALCON-AT.  I really enjoy this game.  It seems to go to great efforts
to duplicate reality.  It even has moving tanks and sam launchers (these
look great up close).  One thing bothers me, though.

It's the afterburners.  Everything I've seen or read has the 'burners
as being an on/off toggle sort of thing.  This game, however, has
"levels of afterburners" using varied amounts of fuel and providing
varied amounts of thrust.  Then, on the cockpit, there is a display
indicating what (if any) level of 'burner is on."

I have looked in F-16 cockpits at airshows and looked through reams of
pictures, but can find no indication of "levels of afterburners" on an
F-16, or any other jet.  The question of the day is:  Is there such a
thing?  Due to the keyboard layout, it makes the game more difficult.
The designers have put so much effort in making this thing fly so well,
why did they insert this kludge (if indeed it is a kludge)?

If there really is such a thing, how does the pilot control the amount
of 'burner, and how is this level displayed?

Thanks,
Tom
------------------------------------------------------------------------
-- 
Tom Basham   	     AT&T Bell Laboratories        (312) 979-6336
att!ihlpb!bash				"If you can't beat 'em, infiltrate
bash@ihlpb.ATT.COM             	         and destroy them from within."
bash@cbnewsd.ATT.COM           

shafer@drynix (Mary Shafer) (06/10/89)

From: Mary Shafer <shafer@drynix>
   Tom Basham (bash@ihlpb.ATT.COM (Basham)} writes:

      I've played a lot of flight simulators on my PC, I even worked on
      military chopper simulators for a while.  Lately I've been playing
      FALCON-AT.  I really enjoy this game.  It seems to go to great efforts
      to duplicate reality.  It even has moving tanks and sam launchers (these
      look great up close).  One thing bothers me, though.

      It's the afterburners.  Everything I've seen or read has the 'burners
      as being an on/off toggle sort of thing.  This game, however, has
      "levels of afterburners" using varied amounts of fuel and providing
      varied amounts of thrust.  Then, on the cockpit, there is a display
      indicating what (if any) level of 'burner is on."

      I have looked in F-16 cockpits at airshows and looked through reams of
      pictures, but can find no indication of "levels of afterburners" on an
      F-16, or any other jet.  The question of the day is:  Is there such a
      thing?  Due to the keyboard layout, it makes the game more difficult.
      The designers have put so much effort in making this thing fly so well,
      why did they insert this kludge (if indeed it is a kludge)?

      If there really is such a thing, how does the pilot control the amount
      of 'burner, and how is this level displayed?


   The afterburner is controlled by the throttle lever.  (Plural A/Bs and
   levers for twin-engine a/c.)  The throttle is on the left side of the
   cockpit and the pilot's left hand rests on it most of the time.  It
   usually has a lot of other switches on it, but the fingerlift for
   engine start is the only powerplant-related one.  The throttle moves
   through an arc.  There are detents for idle power and for military
   power (MIL).  MIL power is the maximum dry (non-burner) power setting.
   To go into burner you just push forward from the MIL-power detent.  If
   you push all the way to the stop you will be in max burner or max
   power.  Between MIL and MAX, you will have varying amounts of burner.

   In the F-14, for example, there are five burner zones.  These are
   rings or zones of spray bars, one behind the other, in the burner.  As
   you advance the throttle in burner, the rings are lit progressively,
   until at max burner you have all five rings spraying fuel into the
   burner.  The British term _reheat_ is very apt.

   The F/A-18 doesn't use the zone terminology, but it does have variable 
   burner settings.  Quoting from the F/A-18 NATOPS manual:
      When the throttle is advanced to afterburner, ignition is turned on,
    the exhaust nozzle opens slightly above the MIL position, the low
    pressure turbine discharge temperature schedule is temporarily reset
    to a lower value, and afterburner pilot spraybar fuel flow and minimum
    afterburner main fuel flow begin.  When afterburner light off is
    detected, ignition is turned off and afterburner main fuel flow
    increases to the level selected by the throttle position.

   The F-15 has stages.  Quoting from the F-15 Dash 1:
      When the throttle [of the F100-PW-100] is moved into afterburner,
    afterburner ignition is activated for approximately 1-1/2 seconds.  
    ...
      The (F100-PW-100) afterburner has five stages that are progressively
    selected as the throttle is moved from MIL to MAX.

   The F-16 is probably just like the F-15.  If your F-16 drogue chute
   deploys in flight and won't jettison, you go to max burner briefly.
   That solves the problem very nicely, but you can't land hot on a short
   runway :-)

   Throttle position is a kinesthetic input to the pilot and throttle
   position is not explicitly displayed. The detents are good indicators
   and the throttle friction is adjustable.  Pushing through the detent
   to burner is quite noticeable.  Engine displays include RPM, exhaust
   gas temp, fan turbine inlet temp, engine pressure ratio, compressor
   and turbined discharge pressure, fuel flow, fuel temp, oil pressure,
   nozzle position, and (estimated) thrust, depending on which a/c you're
   in.  There are also a lot of warnings that will come up on the various
   displays and the HUD.

   A rough approximation of the layout

                               ______   Throttle
                              /      \  
       Aft                    \__ ___/                     Forward
                                //
          _____________________//_____________________________
          |      |                            |              |
         Off    Idle                         MIL            MAX
         Stop   Detent                       Detent         Stop


M F Shafer
NASA Ames-Dryden Flight Research Facility
Ignore the Reply line--I'm really shafer@elxsi.dfrf.nasa.gov

jallred@bbn.com (John Allred) (06/10/89)

From: jallred@bbn.com (John Allred)

In article <7286@cbnews.ATT.COM> bash@ihlpb.ATT.COM (Basham) writes:
>I have looked in F-16 cockpits at airshows and looked through reams of
>pictures, but can find no indication of "levels of afterburners" on an
>F-16, or any other jet.  The question of the day is:  Is there such a
>thing?  Due to the keyboard layout, it makes the game more difficult.
>The designers have put so much effort in making this thing fly so well,
>why did they insert this kludge (if indeed it is a kludge)?
>
>If there really is such a thing, how does the pilot control the amount
>of 'burner, and how is this level displayed?

I can offer some insight, as I help developed an "F-16 like" aircraft 
simulation recently.  According to our co-contractor, the throttle
used in the simulation just like the real F-16 throttle.  At throttle settings
below afterburner, the throttle is very smooth; in the afterburner range,
the throttle had several detents.  Hence, one could select some number of
detents of afterburner.

____
John Allred
BBN Systems and Technologies Corp.
(jallred@bbn.com)

"Argue for your limitations, and you get to keep them." -- R. Bach