<?xml version="1.0"?>
<!-- $Id$ -->
<!--
  Submarine Scout class airship.

  Copyright (C) 2007 - 2009  Anders Gidenstam  (anders(at)gidenstam.org)
  This file is licensed under the GPL license version 2 or later.
-->

<PropertyList>

 <title>Submarine Scout Airship</title>
 <!-- Specific keys -->
 <key>
  <name>d</name>
  <desc>Drop ballast in 5 lbs steps.</desc>
 </key>
 <key>
  <name>D</name>
  <desc>Drop ballast in 50 lbs steps.</desc>
 </key>
 <key>
  <name>W</name>
  <desc>Weigh-off to 50 lb heavy. (Takes about 10 seconds and only works on ground.)</desc>
 </key>
 <key>
  <name>w</name>
  <desc>Show current on-ground weight.</desc>
 </key>
 <key>
  <name>F</name>
  <desc>Open gas valve.</desc>
 </key>
 <key>
  <name>f</name>
  <desc>Close gas valve.</desc>
 </key>
 <key>
  <name>Q/q</name>
  <desc>Open/close fore ballonet outflow valve (closed = nose becomes heavier).</desc>
 </key>
 <key>
  <name>Ctrl-Q</name>
  <desc>Open/close fore ballonet inflow valve.</desc>
 </key>
 <key>
  <name>A/a</name>
  <desc>Open/close aft ballonet outflow valve (closed = tail becomes heavier).</desc>
 </key>
 <key>
  <name>Ctrl-A</name>
  <desc>Open/close aft ballonet valve inflow valve.</desc>
 </key>
 <key>
  <name>U</name>
  <desc>Request ground crew to prepare for landing.</desc>
 </key>
 <key>
  <name>Y</name>
  <desc>Tell ground crew to let go.</desc>
 </key>
 <key>
  <name>R</name>
  <desc>Pull the rip cord. Do NOT use in midair.</desc>
 </key>

 <!-- Handling instructions. -->
 <line>Take-off
 
 1. Weigh-off (W). Small non-rigid airships often take-off slightly heavy.
 2. Tell the ground crew to let go (Y).
 3. Adjust static trim and envelope pressure if needed (q/Q, a/A).
    During take-off the trim should be neutral while in flight the airship
    should be trimmed slightly nose heavy
    for pitch stability at high speed (i.e. above 30 MPH).
 4. Start the engine (magnetos on + s hold intil the engine catches).
 5. Take-off is done at full throttle. Use some elevator to
    keep the nose high.
 6. Maintain pitch trim and envelope pressure by careful use of the ballonet
    valves (avoid permanent elevator deflections).
    The rudder needs constant attention since airships are unstable in yaw.
 7. Remember that the secondary effect of elevators and rudder are quite strong.
    Full elevator up might push the whole airship down at low speed.
 
 Landing
 1. Check static condition: slightly heavy is better than light.
 2. Prepare the ground crew (U).
 3. Approach is against the wind, low (~150ft) and slow.
 4. Aim to arrive between the handling parties, below 100ft and with very low speed.
 5. The ground crew uses the handling guys to secure the ship.

 Envelope pressure and static trim management
   Monitor and maintain the envelope pressure at between 15 - 25mm water (=
   the height difference between the outer and inner fluid in the manometers).
   The ballonet valves are used to keep the pressure and the static trim in
   line. Opening the ballonet outflow valves let air out of the ballonets.
   Air at pressure to inflate the ballonets is taken from the
   propeller slip stream when the ballonet inflow valves are open.

 Moving the ground crew
   The ground crew can be moved via Alt + click. 
 
 Pilot's notes: http://wiki.flightgear.org/index.php/Submarine_Scout
</line>

</PropertyList>
