<?xml version="1.0" ?>
<!--
Description of the Wright Cyclone 972TC18DA3 engine for the Lockheed1049h
Copyright (C) 2015, 2018 Ludovic Brenta <ludovic@ludovic-brenta.org>

This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

References:

http://www.enginehistory.org/Wright/Kuhns/CurtissWrightTC18/TurboCompounds.shtml
http://www.flightglobal.com/FlightPDFArchive/1962/1962 - 2858.PDF

In summary, three versions of the Turbo-Compound engine were offered for the 1049H:

* the 972TC18DA3 rated at 3250hp,
* the 988TC18EA3 rated at 3400hp,
* the 988TC18EA6 rated at 3400hp.

This file models the "low-end" engine.

http://www.airweb.faa.gov/Regulatory_and_Guidance_Library/rgMakeModel.nsf/MainFrame?OpenFrameSet
(FAA certificate, 6a5 revision 25)

Engine performance depends on the impeller ratio, low or high, which the flight
engineer selects with the SUPERCHARGER levers:

Impeller ratio | 6.46:1 (low setting)          | 8.67:1 (high)
_______________+_______________________________+________________________________
  Maximum continuous power at critical altitudes:
sea level      | 49.0 inHg, 2600 rpm (2700 hp) | -
 5800 ft       | 47.0 inHg, 2600 rpm (2750 hp) | -
10050 ft       | -                             | 48.5 inHg, 2600 rpm (2405 hp)
16400 ft       | -                             | 47.0 inHg, 2600 rpm (2450 hp)
_______________+_______________________________+________________________________
  Maximum take-off power (2 minutes at sea level; 5 minutes at 7500 ft.; straight
  line variation of takeoff power time with altitude to 7500 ft.):
Sea level      | 56.5 inhg, 2900 rpm (3250 hp) | -
 5500 ft       | 53.5 inHg, 2900 rpm (3250 hp) | -
13300 ft       |                               | 49.5 inHg, 2600 rpm (2535 hp) 
15200 ft       | -                             | 49.0 inHg, 2600 rpm (2550 hp)
_______________+_______________________________+________________________________

To compute the fuel flow, the same document tell us that:

* the 1049H has a fuel capacity of 6550 gal plus two optional wing tip tanks of
  609 gal each, not modelled here.
* http://www.munich-airport.de/en/consumer/erlebnis/besucherpark/hist_flugz/superconst/index.jsp
  tells us that a 1049G with the same engines and tip tanks had a range of
  4774 nmi @282 KTAS and 20000 ft.
* Knowing that 1 gal = 6 lbs of high-octane fuel, this gives a fuel flow of
  (6550+2*609 gal * 6 lbs/gal)/(4774 nmi/282 kts)=2753 lbs/hour during cruise.
* www.flightglobal.com/FlightPDFArchive/1962/1962 - 2858.PDF says 370 imperial
  gallons/h = 444 gal/h = 2666 lbs/h at a slower 270 KTAS; this is
  almost perfectly proportional to the above, viz. 0.101 nmi/lb.
* So, we tune our engine model to burn 2666/4=666.5 lbs/hour per engine at
  270 KTAS and 20000ft.
* https://en.wikipedia.org/wiki/Lockheed_L-1049_Super_Constellation states
  that the wing-tip tanks increased range by 1770 km or 956 nmi; this gives
  a range for our aircraft of 3818 nmi.

I tuned the figures following http://wiki.flightgear.org/JSBSim_Engines:
volumetric efficiency to get the desired fuel flow, then bsfc to get the desired
power at altitude.

-->

<piston_engine name="Wright Cyclone 972TC18DA3">

  <minmp unit="INHG"> 7.0 </minmp>
  <maxmp unit="INHG"> 29.92 </maxmp>
  <displacement unit="IN3"> 3347.9 </displacement>
  <bsfc>0.251</bsfc>
  <volumetric-efficiency> 0.385 </volumetric-efficiency>
  <maxhp>    3250.00 </maxhp>
  <cycles>      4.0 </cycles>
  <bore unit="IN"> 6.125  </bore>
  <stroke unit="IN"> 6.312 </stroke>
  <cylinders> 18 </cylinders>
  <cylinder-head-mass> 25.0 </cylinder-head-mass>
  <compression-ratio> 6.7 </compression-ratio>
  <sparkfaildrop> 0.9 </sparkfaildrop>
  <idlerpm>   500.0 </idlerpm>
  <maxrpm>       2900.0 </maxrpm>
  <maxthrottle> 1.0 </maxthrottle>
  <minthrottle> 0.1 </minthrottle>
  <starter-rpm>470</starter-rpm>
  <boostmanual>      1 </boostmanual>
  <numboostspeeds>   2 </numboostspeeds>
  <boostoverride>    1 </boostoverride> <!-- allow MAP to exceed rated MAP -->
  <takeoffboost>     0</takeoffboost> <!-- takeoff boost not used because it works poorly. -->

  <!-- Low-speed supercharger; see table above.  The rated boost is on top of
       sea level ambient pressure. -->
  <ratedboost1 unit="INHG"> 23.58 </ratedboost1> <!-- 53.5 - 29.92 -->
  <ratedpower1> 3250 </ratedpower1>
  <ratedrpm1>   2900 </ratedrpm1>
  <ratedaltitude1> 5500 </ratedaltitude1>

  <!-- High-speed supercharger; see table above. -->
  <ratedboost2 unit="INHG"> 19.08 </ratedboost2> <!-- 49.0 - 29.92 -->
  <ratedpower2> 2550 </ratedpower2>
  <ratedrpm2>   2600 </ratedrpm2>
  <ratedaltitude2> 15200 </ratedaltitude2>

</piston_engine>
