Piston Engines
Piston Engines
Piston Engines
Using the altimeter in the cockpit how can we measure "pressure altitude"?
A rich mixture in terms of piston engine fuel system supply to the induction manifold is a mixture of air to fuel.
For maximum endurance the mixture control should be set to:
What is the best method for limiting the effects of vapour locking?
The purpose of the accelerator pump is?
In an aircraft equipped with a float type carburettor and a constant speed propeller, carburettor icing would probably first be detected by
How is a stable idle achieved in the carburettor?
The octane rating of a fuel characterises the :
For piston engines, mixture ratio is the ratio between the :
Which power settings are most likely to promote detonation in petrol engines?
Which statement is correct regarding fuel energy density?
What effect does the mixture fuel-air have on the flame front velocity
On a climb the decrease in pressure causes ....
When the carburettor air intake is in "Hot Air" the power output of the engine is reduced because:
What is the normal indication that a petrol engine is suffering from "Detonation"?
When would a pilot most likely expect carburettor icing?
Tetra ethyl lead is added to some aviation gasoline fuels to:
The colour of Aviation gasoline 100 LL is:
What is the purpose of the priming pump?
What is the purpose of power enrichment in a carburettor?
2 Groups of engines
1. Piston engines 2. gas turbine engines systems
Piston engines 2 arten
a) Unboosted/ Normal aspirated engine b)boosted
Unboosted/ Normal aspirated piston engine
the ambient air is drawn into the cylinder by the piston
boosted piston engines
a charger delivers compressed ambient air (more air mass) into the cylinder
Turboprop
gas turbine driving a propeller to create the thrust force
Turbofan
gas turbine driving a fan that creates thrust force as the reaction force to the acceleration of the air in the nozzle
Grundprinzip Piston engine
The high pressure inside the cylinder during combustion creates a force on typ of the piston, which is transmitted to the crankshaft, creating torque.
Was kann bei inverted cylinders passierenN z.B. beim Sternenmotor
Es entsteht ein Hydraulicing (oil flood) => Oil flows down into the cylinder head and blocks the movement of the piston. This oil must be drained (Säubern) from the cylinder by removing the spark plug before engine start
Welche Piston engines kommen am häufigsten in Airplanes vor?
Horizontal opposed air-colled engines ==> Boxer => 4-6 cylinder
Sternenmotor
Kurbelwellen in der Mitte => Ungerade Anzahl Zylinder ( bei 2-Reihiger Motor = gerade Zylinderanzahl) => Daraus ergibt sich die Zündreihenfolge
Verschiedene Arten Otto-Motoren
a) Reihenmotor b) V-Motor (Nockenwelle entscheidet, ob schneller oder langsamer Motor) c) Boxermotor (jeder Zylinder hat 2 Kerzen
vgl Bild
1) Zylinder 2) Kurbelwelle (Crankshaft) 3. Kurbelgehäuse (Crankcase) 4. Heat exchange
vgl. Bild
1. Vc (Clearance Volume) 2. TDC Top dead centre 3. bottom dead centre 23. Distance: length of stroke 4. Piston 5. Connecting Rod 6. connecting rod force 7. Crankshaft
Torque
F Rod * Arm F Rod= Connecting rod force
V Total im Zylinder
Vc + Vs = Vt Vc = Clearance Volume = Between TDC and the top of cylinder Vs = displacement between TOD and BDC
Compression ratio
\(Compression ratio = {Vs + Vc \over Vc}\)
Stroke
Distanve between TDC and BDC
Long Stroke engine where teh sroke is greater than the piston Bore (Zylinderbohrung) führt zu ?
Kraft mal Arm ist hier grösser => Grösser Tork
Short Stroke Engine where the stroke is less than the piston bore ist der Fall, wo?
Bei Rennmaschinen
3 factor for the power output of a single cylinder engine
1. Weight of air mixture taken in (Wie viel Gemisch) 2. Amount of compression 3. Number of working/power strokes per Minute = Drehzah
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Cartes-fiches
Hohe MAP => ?
der totale Druck => Hohe Leistung
Precision fuel pump?
Einspritzung wird durch die Pumpe bestimmt, bei den anderen durch den Luftdruck
Flame Rate ? Difference Verbrenne und Explosion/Detonation ?
50 - 80 ft/sec => Beim verbrennen kont. Druck, explosion explosionsartiger Druck
Frühzündung
vor den 25 Grad vor dem OT ==> Gibt sehr grosse Drücke => muss man verhindern
Was führt zur einer Explosion/Detonation?
mixture lean, high MAP, falsches Fuels, expired fuel, high engine temp., hot intake air
Flared fin
Kühlung Luft => Luft wird beschleunigt und dadurch wird kalte Luft angesogen
Augmenter Tube?
Schachtelung => Durch die Schachtelung wird etwas kalte Luft angesogen
Cowl flaps open/closed?
open: Taxi, T/O, climb closed: Cruise, Descent, Landing
Für was haben wir die Exhaust gas temperature ANzeige?
Das wir richtig mixen können
Darf man die Vergaserwärmung am Boden benützen?
Nein, weil sonst ungefiltert Luft reinkommt
Wann bildet sich am besten Ice bei der Throttel Klappe?
Wenn die Throttellappe nur ein Bisschen geöffnet ist, weil die selbe Luftmasse durch einen kleineren Durchgang muss, wird sie beschleunigt
superchargers
Überlader => wir laden über das vorgesehene Volumen => Driven by the Crankshaft via the Gearbox, that compress air/fuel mixture delivered from the Carburetor
Bis wo kann der Turbocharger seinen Druck halten ?
Bis zu einem gewissen Druck => Critical Altitude
Wie wird die Critical Altitude bestimmt?
Throttelklappe voll geöffnet und Wate gate Klappe zu ==> Alle Abgase gehen in die Turbine
Wie funktioniert das Waste Gate?
Wenn wir steigen, desnity nimmt ab --> deckpressure nimmt ab -> Nadel geht nach oben --> nicht mehr so viel Oil kann durch fliessen --> Oil Druck nimmt zu = Waste Gate geht zu!!!
Bis zu dem Punkt, wo trosselklappe voll offen und Waste Gate zu --> Critical Altitude Wenn wir weiter steigen, füllen sich Zylinder nicht mehr ganz, weil Druck nimmt ab
Wenn Waste Gat voll offen?
wenig Power => schützt jedoch den Motor
Was macht das indirect fuel injection system nicht im vergleich zu carburettor?
the indirect fuel injection system does not adjust the required fuel to air mixture automatically like a float type carburettor => mixture constant by 1:10
Constant speed propeller ?
It is controlled with the prop (RPM) lever from the cockpit where a RPM is selected that is then constant => keeps the RPM constant regardless if you change the airplane attitude. The propeller governor changes the propeller pitch and therefore the propeller drag required to maintain the RPM
How can the Prop maintain the RPM?
a) a spring force to deacrease the propeller pitch which is counteracted by? b)
b) a variable oil pressure force to increase the pitch
What happen by the T/O (constant speed propeller)
- engine RPM increases
- fly weights lift governor piston
- oil is directed to the propeller hub
- piston moves the propeller to higher pitch
- more propeller drag (tangential force) reduces the RPM
- less fly weight force
- the speeder spring moves the governor piston down , which stops the oil flow
==> This accelerates teh aeroplane until thrust is equal to aeroplane drag
Increasing aeroplane speed (constant speed aeroplane)
- TAS increases
- AOA of the propeller decrease
- Prop rotationsaö draf decreases
- RPM increases
- pitch-changing mechanism of teh constant speed propeller increases pitch
- RPM is the same as before
the higher propeller pitch will fit the increasing TAS, resulting in optimum acceleration
Wind milling with a constant speep propeller
while the constant speed propeller windmills, the governor pump up enough oil control pressure to allow the pilot to change the pitch
MAP: engine not running: MAP indication?
MAP indication will show the state ambient pressure
MAP: enginne running, throttle fully open MAP indication?
MAP is slightly lower than the ambient pressure because the piston is drawing air into the cylinder
Engine running, throttle at nearly closed position MAP indication?
MAP shows the lowest value because the engine draws air though a nearly closed throttle valve, creating suction
What happens with increasing altitude (MAP)?
with increasing altitude and full throttle, MAP and power drop due to decreasing density
Critical Altitude and Full Throttle Height
the pressure altitude up to which a certain power setting can be maintained ==> RPM + MAP
Rated ALtitude
the altitude up to which the Max. continuous power can be maintained
Compression rings are located at:
An eight cylinder horizontally opposed engine will have a firing sequence every:
What is the main advantage of using a wet sump oil system.
Immediately after engine starting which normal indications would we expect to see in the cockpit?
Oil returning to the oil tank is filtered by:
What are the main advantages of a dry sump system?
An oil pressure relief valve is fitted to:
During combustion a piston engine produces most heat on the power stroke. Which single component removes most heat from the combustion chamber
What is the correct method of checking that an aircooled piston engine is operating at the correct temperature?
The firing order for a typical four cylinder horizontally opposed aircraft piston engine is:
Which statement is correct? A Impulse Coupling Starter is.
How is the spark retarded for starting using a magneto?
