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Beagle Pup

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Beagle Pup 100/150/160
Beagle Pup 100.png
Type Light aircraft, Trainer aircraft, Sport aircraft, General aviation, Historical aircraft
Configuration Low wing aircraft
Propulsion Piston aircraft, Single-engine aircraft
Manufacturer Beagle Aircraft Limited
Author(s) Richard Senior
--aircraft= pup100

Status Alpha
 FDM Stars-2.png
 Systems Stars-2.png
 Cockpit Stars-2.png
 Model Stars-2.png
 Website The website for the Beagle Pup 100/150/160 developments.
 Repository The development repository of the Beagle Pup 100/150/160.
Download Download the Beagle Pup 100/150/160 aircraft package for the current stable release (2018.3).
License GPLv2+

The Beagle 121, better known as the Beagle Pup is a light sport and general aviation aircraft designed and built during the 1960s by Beagle Aircraft Ltd at Shoreham and Rearsby in the United Kingdom.


Series 1 (Beagle Pup 100)

Powered by a 100hp Rolls-Royce Continental 0-200 engine, the original Beagle Pup has modest climb rates of around 500 ft/min and a cruise speed of 90-95 knots (TAS). Fuel capacity 24 imperial gallons (29 US gallons).

Series 2 (Beagle Pup 150)

The Pup 150 retains the same airframe as the Pup 100 with an enlarged and reshaped engine cowl to accommodate a 150hp Lycoming 0-320-A2B engine. The extra power allowed for additional passenger seating in the rear and produced climb rates of around 800 ft/min and a cruise speed of around 115 knots (TAS). Fuel tanks were unchanged from the Pup 100, although there was an option for additional tanks to increase the capacity to 34 imperial gallons (41 US gallons).

Series 3 (Beagle Pup 160)

The Pup 160 has exactly the same airframe and cowl as the Pup 150, but was fitted with fuel tanks totalling 34 imperial gallons (41 US gallons) as standard and powered by a 160hp Lycoming 0-320-D2C engine. Cruise speed and climb rates are comparable to the Pup 150, the Pup 160 is really about increased range and carrying capacity.

The most common aircraft currently in use is the Pup 150. Only a handful or Pup 160s were made before Beagle went into liquidation and most were exported from the UK. The Pup 100 is considered to be slightly underpowered.

Flight Notes

The aircraft is still in an alpha state but completely flyable from the 3D cockpit. The external model is currently of a Pup 100 for all three variants and the 3D cockpit, while having many of the correct instruments, has a temporary layout.

Systems are relatively mature, including fuel and electrical systems. Autostart executes the startup checklists and puts the aircraft in a ready for taxi or takeoff state, depending on starting location. Some basic cockpit lighting is provided for night flying.

Takeoff with the first step of flaps, full power and rotate at around 60 knots. Raise flaps around 300ft AGL and trim for steady climb rates of around 500fpm for the Pup 100 and 800fpm for the Pup 150 and 160. Adjust mixture for maximum RPM to maximize rate of climb. When approaching cruise altitude, lean mixture to 50*F rich of peak (which should be where the asterisk is on the EGT gauge), level off and adjust throttle for 2500rpm.

Approach at around 80 knots, with power reduction to around 1800rpm and the first step of flaps lowered prior to the base turn. Mixture full rich and carb heat hot. Landing speed is around 70 knots with landing flaps lowered on final to bring the nose down for a better view of the runway.

The checklists are 95% accurate with respect to normal operating procedures. Performance, including fuel consumption, is within 10% of quoted at level speeds at various altitudes and RPMs. The FDM is a stock Aeromatic++ FDM tuned to performance specifications.

There is a continuous fuel simulation, i.e. it saves the fuel levels on exit. Check fuel before you fly.

Note  A bug introduced in v0.22.2 caused incorrect adjustment of payload weights. This is fixed in 0.23.1 but it is recommended to delete the saved state in FG_HOME/aircraft-data/pup*.xml to avoid unexpected changes to center of gravity and aircraft stability.

Table of V Speeds

Designator Description IAS (knots)
VS0 Stall speed in landing configuration (landing flaps) 54
VS Stall speed in cruise configuration (no flaps) 63
VRef Landing reference speed (1.3 x VS0) 70
VFE Maximum flap extension speed 100
VNO Maximum speed for normal operations 120
VNE Never exceed speed 150

Icing Simulation

Carburettor Temperature

Available from aircraft version 0.17.0 onwards

This feature is off by default and enabled through the Beagle Pup | Preferences menu. Without the checkbox checked, carburettor temperature is simulated and displayed on the cockpit gauge but no icing will occur. Checking the checkbox turns the icing simulation on. Note that ice is not cleared by unchecking the box; if you turn the icing simulation off while you have carb ice, it will not thaw! The setting is saved on exit, but note that the Pup 100, 150 and 160 are different aircraft and each have their own setting.

The checklists guide you through the process of introducing carb heat to prevent icing. In short, this means applying carb heat when idling on the ground and during taxi, turning off when full power is applied prior to takeoff, and re-applying when power is reduced for descent. Note that if you use autostart for a runway start, the carb heat control will be in the off position ready for immediate takeoff. If you sit on the runway with idle throttle for a more than a few seconds, the carburettor is likely to ice up and reduce your takeoff power.

Carb icing may occur during cruise if weather is cool and damp, so watch the carb temperature gauge and apply just enough carb heat to keep the temperature above the yellow zone. The outside air temperature gauge gives an indication of the likelihood of icing conditions and you should pay attention to the dewpoint from enroute weather observations as an indication of humidity. Applying carb heat reduces engine power so only apply as much as is required to prevent icing.

Continental engines, as fitted to the Pup 100, are more prone to carb icing than the Lycoming engines fitted to the Pup 150 and 160. This is because of the mounting position of the carburettor relative to the engine. With the Pup 100, you are more likely to need carb heat during cruise. For both engines, once the engine is warm, the likelihood of carb ice is reduced, but less so with the Continental engine.

The symptom of carb icing is reduced power as the ice buildup constricts the air intake of the carburettor. It has the same effect as closing the throttle. To clear the ice, you need to increase the temperature of the carburettor above freezing, usually by applying carb heat. This diverts hot exhaust gases to heat the carburettor. You can also prevent or clear carb ice to some extent by warming the carburettor in other ways; increased throttle to reduce the venturi effect that causes carb cooling, or proper leaning of the mixture.

Pitot Temperature

Available from aircraft version 0.28.0 onwards

As per the carburettor icing, this feature is off by default and enabled through the Beagle Pup | Preferences menu. The same comments apply regarding turning off the simulation when the tube is iced.

Pitot heat should be applied when flying in freezing conditions with high levels of moisture present. Icing is most likely to occur when descending from freezing temperatures through warmer moist air, so remember to apply pitot heat before descent. The pitot heater is switched on using the rightmost circuit breaker on the electrical panel.

The symptom of pitot ice is a steady reduction in indicated airspeed. The simulation reduces the pressure reported by the pitot system which in turn affects the airspeed indicator. When icing reaches its maximum level, the tube is simulated as blocked, i.e. the water drain hole is plugged as well as the tube. This causes the pressure reported by the pitot system to remain constant and the airspeed indicator, driven only by the static system, behaves like an altimeter. Applying pitot heat clears the ice in a couple of minutes and the airspeed indicator should return to normal. Pitot heat should be turned off when moving slowly, i.e. when taxiing, to avoid overheating the pitot tube, but this is not yet simulated.

Sperry SP Series Autopilot

The Sperry SP autopilots consisted of a series of modules that could be added individually to an aircraft to provide different degrees of autopilot control. Note the white blanking plates at the bottom of the autopilot controller, which are placeholders for a series of control buttons.

The most basic configuration -- the SP1 -- is simply a yaw stabilizer, controlling only the rudder. The SP2 systems are two-axis autopilots, controlling aileron and elevator. The full set -- designated the SP3 -- is a three-axis autopilot with altitude hold and automatic heading hold. I have seen photographs of later units with a complete set of four buttons on the controller: HDG HLD, ALT HLD, NAV LOC and GLD HLD but I am not aware of Beagle having fitted these to any aircraft.

Sperry SP3 in the Beagle Pup

Judging by photographs, publicity material and existing aircraft, Beagle did not fit an autopilot to the Beagle Pup as standard. During the time the Beagle Pup was being manufactured, they were fitting Sperry SP3 autopilots to the Beagle 206 (Basset). Rather than use the generic Flightgear autopilot, I've taken the opportunity to satisfy my appetite for obscure autopilot controllers by modelling the Sperry SP3 for the Beagle Pup.

The SP3 is a three axis autopilot, controlling pitch, roll and yaw. If you are flying the Beagle Pup with auto-coordination turned on, the autopilot does not attempt to control the rudder, so technically you are flying with a Sperry SP2A and Flightgear is dealing with coordinated turns.

Controls are basic. There is a pitch wheel to control pitch, a turn knob to control roll, an altitude hold button and an on off switch. Trim controls are also provided for the pitch and roll channels. Note that these are not direct controls of aileron or elevator trim, these are autopilot trims. There is no button or switch for heading hold, and no heading bug; heading hold is automatic when a neutral turn is selected. There is no automatic tracking of a VOR radial, no glideslope coupling and the autopilot does not follow a route-manager route.

Control of pitch is fairly self-explanatory. When the autopilot is turned on, it will attempt to stabilize the aircraft at the pitch that is set on the wheel. So if you turn the autopilot on during climb, you will want to preset a positive pitch on the pitch wheel of about 4-5 degrees. With the pitch wheel at zero detent (use the help text in the bottom left corner of the screen) the idea is that the aircraft should fly level. It probably won't, which is why there is an "Elev. Trim" knob. With the aircraft at a typical cruise altitude and power (leaned if necessary), adjust the elev trim knob so that a selection of zero pitch on the main pitch wheel produces level flight. This trim setting is saved when you exit Flightgear but may need adjusting based on fuel and payload. Once the pitch axis is trimmed, with the pitch wheel centered, you can press the "ALT HLD" button to hold the current altitude. Altitude hold is cleared when you rotate the pitch wheel away from center and needs to be pressed again to hold a different level.

Control of roll is also quite simple. As with the pitch channel, trimming may be necessary. The turn knob allows left/right turns up to 20 degrees of bank, which produces a standard rate turn. With the turn knob centered, the aircraft is supposed to fly wings level and, if the heading is stable, will lock onto the stable heading. If you center the turn knob and the aircraft doesn't lock onto the heading, use the roll trim wheel to cancel out any turn due to imbalance of the aircraft. Again, the trim is saved on exit and screen help indicates the amount of turn you have selected and also the heading hold. It takes less than 2 seconds to lock the heading after selecting zero bank.

There are no controls on the controller for the yaw channel. Coordinated turns are handled by the autopilot if auto-coordination is turned off. If you are flying with mouse or keyboard control and the autopilot is controlling yaw, you will want to center the rudder before engaging the autopilot, and particularly before attempting roll trim. Currently the only way to do centre the rudder is by using the HUD.

Without a heading bug, establishing a heading takes a little practice. The key is that the autopilot is tuned to roll level from half the bank angle from your target. So, for example, if you are flying at 270 and you want to fly a heading of 360, establish a full right turn with the turn knob (20 degrees of bank) and, just before 10 degrees from your target, i.e. 350 degrees, center the turn knob. The turn knob uses a standard knob/slider animation, so holding down the shift key and left-clicking banks right in 10 degree increments. Shift middle-click banks left. The controls are heavily filtered to keep these turns smooth. Fine-tuning a heading, e.g. when tracking a NAV radial, is easily achieved by clicking the turn knob a couple of times to bank slightly left, then middle-clicking a couple of times to center again.

Ctrl-z toggles the main autopilot on/off switch and Ctrl-a toggles the altitude hold button, which will only work iff the pitch wheel is at its center detent position. Other conventional autopilot shortcuts, e.g. Ctrl-h, Ctrl-g do not work with this autopilot.

Development Status/Issues


There are some issues with keyboard control and flight characteristics outside of the normal flight envelope. Stalls near the ground are lethal. Behaviour in moderate to fresh crosswinds and above (> 15kts) is troublesome on the ground.


Each variant has a handful of liveries for testing purposes. If you want to make your own liveries for this aircraft, be aware that the exterior model is unfinished and likely to be remapped. Any existing liveries will become invalid at that point.

External links