Robin DR400/140B Supplementary Information

Brand: Robin

Model: DR400/140B

Category: Engine

Type: Supplementary Information

NOORDZEE VLIEGCLUB OOSTENDE

DIESEL POWERED ROBIN

DR400/140B

Supplementary information

Remark:

This text is for info only, not to be known by heart, but it helps to

understand the Diesel engine. May help you to fall asleep as well.

INFORMATIONS BASED ON SUPPLEMENT PILOT’S OPERATING HANDBOOK

AND SUPPLEMENT AIRPLANE MAINTENANCE MANUAL PUBLISHED BY

THIELERT AIRCRAFT ENGINES GmbH

Met bijzondere dank aan de collega’s van de RAAC voor het ter beschikking stellen van de

informatie ( F. Gardin –voorzitter NZVC)

Revision History:

V0.1 Initial text - Luc Sobry

V0.2 Initial editing - Danny Cabooter

V1 Some items in description set in bold to draw attention - Marc Teugels

Various layout changes - Marc Teugels

V2 Syntax and grammar review – Paul Hopff

System descriptions corrected – Paul Hopff

Aanpassingen voor NZVC OO-NZV – Gardin Franky

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INTRODUCTION

The Robin DR400 is originally fitted with a gasoline Textron Lycoming power plant developing 160

BHP at 2700 RPM. It features four horizontally opposed cylinders and is of the normally aspirated,

direct drive, air cooled type. The engine, the O-320-D2A, is coupled to a Sensenich two-bladed metal

propeller.

Because of the soaring prices of aviation gasoline, the NZVCgot interested in the recent

developments of the diesel technology for light aircraft. Thielert Aircraft Engines GmbH

[HOP1]obtained

a STC

1 to install their TAE 125-01, a diesel engine, but which also operates on Jet A1 fuel (kerosine),

along with a new, three-bladed propeller in composite material manufactured by MT Propeller

Entwicklung GmbH. Both diesel fuel and Jet A1 are considerably cheaper than the usual 100LL

gasoline. In addition, both turn out to be less inflammable, thus reducing the fire risk in case of

mishap. This retrofit entails in turn a few changes in other aircraft systems, as well as in the basic

weights and performance.

Assuming that you read the “Aircraft Flight Manual Supplement” further simply referred to as the

“Supplement”, you have probably noticed that this text is rather superficial, sometimes a bit obscure,

and it even contains some errors once in a while. Although this compilation attempts to explain or

clarify a few things, the “Supplement” mentioned above remains the only official document. In

addition, you will find a questionnaire which may help you in testing your knowledge on the subject.

DIESEL ENGINE GENERALITIES

Present day diesel and gasoline engines are usually operated according to the four stroke cycle:

induction, compression, expansion and exhaust. The major difference in a diesel engine, is that the

cylinder(s) do not compress a fuel/air mixture as is the case in the gasoline version, but solely air.

Typical for diesel engines is that there is no throttle valve. During the induction stroke, the air can

freely enter the cylinder. Unlike in gasoline engines where the fuel/air mixture must be very carefully

metered, diesel engines operate with an excess of air which, amongst other things, significantly

contributes in reducing smoke emissions. Furthermore, as solely air is compressed, no detonation and

engine knocking can occur.

Incidentally, due to the absence of a throttle valve, the lever often referred to as the throttle lever is

no throttle lever at all: it is a thrust lever through which only the fuel injection at the end of

the compression stroke may be caused to vary, thus regulating the load and RPM

conditions.

Compared to the gasoline engine, the compression ratio in a diesel is much higher. For the TAE 125-1

it is 19/1 or 18/1 (depending on the serial number), i.e. more than twice the value of the original

power plant, thus raising the temperature of the induction air to such a high value that, once fuel is

injected under very high pressure in the cylinder, it ignites spontaneously. This means that a diesel

engine does not require an ignition system, i.e. neither spark-plugs nor magnetos and the associated

intricate wiring system. Consequently, there is no need to be afraid of spark-plug fouling

during taxi, which may be carried out at idle power without any problem.

Note that in a diesel engine, as the fuel is always injected in the cylinders, there is no such a thing as

a carburettor, and thus no risk of carburettor icing either. Nonetheless, if carburettor icing is

non-existent, airframe icing is still likely to occur. Unlike the original Textron Lycoming which features

an automatic spring-loaded door against this condition, the TAE 125-1 is fitted with an alternate

air door, located at the induction air inlet filter and controlled by a knob on the

1 Supplemental Type Certificate

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instrument panel. This knob, labelled “ALTERNATE AIR”, should be pulled out if significant

airframe icing happens to be encountered during flight.

No fuel priming is required for engine start and furthermore, as we will see, there is no mixture

control to be taken into consideration.

Perhaps the most interesting part is the fact that the required fuel is diesel (DIN2 EN590), which may

be obtained at any car station-service and which is considerably cheaper than the usual aviation

gasoline. It is unfortunate that, at least presently, few airports (if any) are equipped to provide diesel

fuel. However, as said previously, the TAE 125-01 operates equally well on Jet A1 fuel (ASTM

3 1655),

which is normally available at any major or regional airport. On the other hand, assuming that

diesel fuel would ever be used, one must remember that the fuel temperature in the tank

must be closely monitored, before takeoff as well as during flight to avoid formation of

paraffin (see below).

At any rate, keep in mind that whenever a refuelling stop is required elsewhere than at the

home base, make sure that you don’t plan a stop at an airfield where these fuel types are

not available!

THE TAE 125-01 ENGINE AND ITS PROPELLER

Although most light aircraft engines feature four or six horizontally opposed cylinders, the TAE 125-

01, also referred to as the CENTURION 1.7, has four cylinders in line with double overhead camshaft

(DOHC). In fact, the engine is based on the Mercedes Series A automotive design.

Another major difference is that, unlike most light aircraft engines which are air-cooled, the TAE 125-

01 is liquid-cooled. This, in turn, results in a significant change, not only in the engine’s cooling

system, but in the cabin heating system as well (see below). The power plant also includes a

turbocharger.

Let us first clarify the term “double overhead camshaft”, and have a few words about the

turbocharger:

Double overhead camshaft

Without digging in the constructional details of engines, recall that each cylinder is fitted with (at

least) two valves: the inlet valve and the exhaust valve. Incidentally, the

TAE 125-01 features four valves

per cylinder: two for the inlet, two for the exhaust. The four valve

configuration contributes amongst other things to a lesser fuel consumption and to an improved

quality of the exhaust gases. All these valves are driven by cams (NL: nokken) located on a shaft, the

so-called camshaft (NL: nokkenas) which is itself driven by the crankshaft (NL: krukas).

The camshaft can be located either in the lower part of the engine, close to the crankshaft (NL:

onderliggende nokkenas), or higher up, close to the cylinder head, in which case one talks about an

overhead camshaft (NL: bovenliggende nokkenas), or OHC, operating all inlet and exhaust valves in

the required sequence. Double overhead camshaft, or DOHC, means that two overhead camshafts are

used: one which operates all inlet valves and one which operates all exhaust valves.

Turbocharger

A turbocharger is in fact a form of supercharger and has the very same purpose, namely to increase

the amount of air flowing in the induction system, thus increasing the manifold air pressure (MAP),

and consequently the total power output of the engine. Note that with the TAE 125-01 installed, the

: Deutsche Industrie Norm

3 : American Society for Testing and Materials

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induction air inlet and filter is not longer located on the lower part of the front engine cowling (this is

now for cabin heating purposes), but on the rear upper right hand side of it, as seen from the cabin.

The main difference between a turbocharger and a supercharger is that the latter is mechanically

driven by the engine crankshaft, whereas the former is driven by the exhaust gases acting on a

turbine which, in turn, drives a compressor through which the induction air passes on its way to the

cylinder inlet valves. As this compressed air reaches considerable temperatures, an additional

intercooler is often located downstream of the compressor. The TAE 125-1 features such an

intercooler, the cooling outside air originating from the right upper inlet in the front of the engine nose

cowl, as seen from the cabin.

Turbochargers are fitted with a so-called waste-gate which can either be fixed or of the variable type,

either manually, or automatically by hydraulic or, as is the case for the TAE 125-01, mechanical

means. The waste-gate is a valve which offers free passage to a part of the exhaust gases on their

way to the exhaust, while another part of the gases is deviated towards the turbine driving the

compressor. In the variable type, the wastegate is modulated (usually automatically) in order to admit

more or less gases to the turbine, depending on the density altitude and the power setting.

Turbochargers are compact pieces of equipment. However, as they can reach rotation speeds in

excess of 100000 RPM, they are liable to become extremely hot. This is the reason why, whenever a

turbocharger is installed, the temperature of the exhaust gases must be kept in check and may not

exceed a maximum value, which is 900°C for the TAE 125-01. Nonetheless, as the temperature

regulation of the exhaust gases is automatically taken care of, you will not find an EGT (exhaust gas

temperature) indicator on the instrument panel.

One might rightly believe that the basic purpose of the addition of a turbocharger is to allow higher

cruising altitudes. With the TAE 121-1 engine, it is only 16500 ft for the Robin 135CDI. So, why a

turbocharger? Fact is that many diesel engines perform well without it, but lack somewhat “spirit”.

The main reason for the turbocharger is to increase the volumetric efficiency of the cylinders. In other

words, the more air can be crammed into the cylinders during the induction stroke, the greater will be

the power output. In addition, the presence of an intercooler, located downstream of the compressor,

contributes even more to improve efficiency. Indeed, compressed air heats up and tends to expand

when leaving the turbocharger, but the cooling effect of the intercooler significantly reduces its

volume, thereby increasing its specific mass which leads to a greater weight of air entering the

cylinders at each induction stroke. Both the turbocharger and intercooler, in association with the

constant speed propeller system (see below), contribute to the fact that the performances of the

diesel equipped Robin are fairly close to the original aircraft, despite the considerable lower HP rating.

The engine develops 132.8 HP at 2300 RPM (propeller RPM). However, the propeller is not driven

directly by the crankshaft but through a gearbox whose purpose it is to reduce the

propeller RPM by 1.69. This means that if the propeller RPM is 2300, the crankshaft

rotates in fact at 3887 RPM. In other words, if the TAE 125-01’s propeller would rotate at the

same speed as the crankshaft, i.e. nearly 4000 RPM, the noise would probably exceed tolerable values

and the propeller efficiency would suffer severe losses at the tips.

Besides being driven by the gearbox, and despite the fact that only one single thrust lever is available

on the control pedestal, the propeller is referred to as a constant speed type. Perhaps this calls for

some explanations:

1°) The usual constant speed system implies a variable pitch propeller, i.e. a propeller whose blade

angle can be changed (see PILOT NOTES). A propeller lever allows the pilot to select a chosen RPM

for a selected manifold air pressure, or MAP, which is set by means of the throttle. Variable pitch

propellers are mostly fitted with a so-called constant speed unit, or CSU. The CSU is controlled by

normal engine oil. It includes a flyweight and valve system which ensures that, once a certain RPM

value has been selected for cruise, this value remains unchanged even when the aerodynamic forces

on the propeller vary, hence the term “constant speed propeller”. Remember that on a fixed pitch

propeller, i.e. a propeller whose blade angle cannot be changed, if you increase speed by diving the

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RPM increases, if you decrease the speed by pitching up, the RPM decreases whereas, with a constant

speed propeller, the RPM remains unchanged because the CSU automatically varies the propeller

blade angle so as to maintain the RPM unchanged.

2°) As said, with the TAE 125-01 there is no propeller lever available to the pilot. Here, the CSU is a

system which has been developed by Thielert Aircraft Engines. A pump delivers oil from the gearbox

to the CSU. Incidentally, gearbox oil is NOT the same as the engine oil (see below). Within the CSU,

the oil passes first through a micro-filter, then a pressure relief valve which regulates the oil pressure

to 20 bar prior to reach the propeller control valve (more or less similar to the valve system

mentioned previously) which varies the blade angle. The propeller control valve is electronically

(FADEC) controlled. In other words, the pilot has no propeller lever and consequently, has no control

over the propeller RPM, at least no direct control, as is the case with usual constant speed systems.

3°) If you have a look at the “CRUISE PERFORMANCE, RANGE AND ENDURANCE” chart (page 5-9 of

the “Supplement”), you will notice that the propeller RPM value is not mentioned. Only the percent of

load, in fact the percent of power which is selected by means of the thrust lever, is indicated for

various pressure altitudes, together with the resulting KTAS, the fuel flow in litres per hour, and the

nautical air miles (NAM), i.e. the range under no wind conditions. At any rate, assuming that you

cruise at 2000 ft pressure altitude and at 50% load, you will obtain about 1840 RPM, at 60% about

1960 RPM, at 80% about 2140 RPM, etc… and at 100% 2300 RPM. This implies that, although the

pilot cannot change the propeller RPM at all, the FADEC produces the most efficient blade setting for

the selected load.

Two final remarks:

1°) During the external inspection, you will probably notice that the engine exhaust pipe shows

some play whereas, on gasoline engines, it is supposed to be absolutely fit in a rigid way. On

the TAE 125-1, this somewhat flexible mounting is intentional to the purpose of dampening all

sorts of mechanical vibrations, which are usually much stronger in diesel power plants than on

their gasoline counterparts, and which you will probably notice during engine start, and even

more during engine shutdown.

2°) As the propeller is three-bladed and made of composite material, when manoeuvring the aircraft

on ground with the towbar, great care must be taken not to damage the blades.

THE FUEL SYSTEM

Refuelling procedure

At EBOS airport, Jet A1 is available via Jet A1 refuellers.

When closing the filler cap, a locking device ensures that the cap is secured.

Following each refuelling, the amount of loaded fuel MUST be written in the aircraft’s log-book (as per

checklist). As said before, the most usual fuel is Jet A1 but, assuming that common diesel fuel should

ever be tanked, it is IMPERATIVE that this fact is CLEARLY indicated in the aircraft’s log-book together

with the fuel loaded. Indeed, the limiting temperatures of diesel are much more acute than for Jet A1

(see below) because diesel fuel tends to form paraffin which is likely to block filters at lower

temperatures.

Fuel tank

Except for additional sensors providing fuel temperature readings on the instrument panel, the fuel

tank provides a total capacity of 110 l including 1 l of unusable fuel.

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Fuel temperature limitations

According to the “Supplement”, assuming Jet A1 fuel, the minimum permissible fuel

temperature in the fuel tank before takeoff is -30°. For diesel, this minimum must be

above 0°C. On the other hand, minimum permissible fuel temperature in the tank during

flight is -35° for Jet A1, against -5°C for diesel. It is thus obvious that using diesel might

lead to problems if temperatures are not carefully monitored, particularly during

wintertime.

Diesel and Jet A1 may be mixed. However, as soon as the proportion of diesel in the tank

is more than 10%, or if there is uncertainty about which type of fuel is in the tank, the

fuel temperature limits for diesel operation must be observed.

Fuel circuit, common rail, direct injection

With the advent of electronic control, and provided that direct diesel injection is used, as is the case

for the TAE 125-01, the common rail technology can be applied to further improve the quality of the

exhaust gases, to reduce noise and to further reduce fuel consumption, as compared to conventional

diesel engines.

1°) The electric pump, originally installed for priming purposes only, must be “ON” for

takeoff and landing. According to Thielert, the electrical pump “supports the fuel flow to the fuel

filter module, if required”; according to Maintenance a possible reason is that the high pressure pump

(see below) is located on the far front of the engine, which is why the electrical pump acts as an

additional safety in case of failure of the engine driven fuel pump feeding the high pressure pump. At

any rate, no fuel pressure indicator is located on the instrument panel.

2°) From the fuel tank, the fuel goes through the fuel selector to a small reservoir (probably a

remainder from the original gasoline system), then through the shutoff valve via the electric pump.

Thus far, the system is similar to the original one, except for the fact that, for takeoff and

landing, the electrical pump must be “ON”.

3°) Beyond the shutoff valve, the fuel is ducted towards a so-called filter module which includes a

fuel pre-heater system. This pre-heater, typical for diesel engines, is thermostatically controlled to the

effect that the fuel is heated until the operating temperature of 60°C is reached. The heating is

obtained by exchange between excess fuel returning to the tank (see below) and the cold

supply fuel.

4°) Downstream of the filter module, a camshaft driven pump, i.e. the engine driven pump, increases

the fuel pressure to 5 bar (72 lbs/sq.in.), after which a high pressure pump, also camshaft driven,

further increases the pressure up to 1500 bar (21700 lbs/sq.in.), and delivers the fuel to a duct known

as the common rail.

5°) The common rail acts as a sort of high pressure accumulator which supplies all cylinders (hence its

name) through an equal number of injector duct connections, and contains highly pressurized fuel

ready for injection at any required moment. However, an electronically (FADEC) actuated pressure

control valve in the common rail, lowers its internal pressure to a maximum of 1350 bar (19500

lbs/sq.in.). This gives way to an excess of fuel which is returned to the tank.

6°) The fuel injectors, whose operation is also electronically (FADEC) controlled, deliver highly

pressurized fuel into the combustion chamber of each cylinder. This is known as direct diesel injection,

or DI, as opposed to the indirect diesel injection, or IDI.

In the IDI system, the fuel is initially injected either into a swirl chamber or into a so-called

prechamber, located in the cylinder head, prior to enter the usual combustion chamber in the cylinder.

In a way, in both these “sub-systems”, the combustion chamber is divided in two parts. Both swirl- or

pre-chamber have their own specific advantages and disadvantages which will not be discussed here.

Versie oktober 07

As for the difference between the DI and IDI, here again, both have their own advantages and

disadvantages. For instance, amongst other things, the DI tends to produce more noise, more

vibrations and more harshness than the IDI. On the other hand, the DI gives way to a lesser fuel

consumption than IDI. However, the use of the common rail technology, which seems to be only

applicable for DI, tends to combine the advantages of both DI and IDI.

FUEL SYSTEM

With the TAE 125-1 installed, only two draining points are to be found, a main tank drain valve and a

fuel drain valve.

OIL SYSTEMS

The TAE 125-1 includes two separate oil systems, one for the engine, and one for the gearbox, each

system requiring its own very specific type of oil. Be aware that these oils are not available at the BP

refuelling services at Antwerp/Deurne airport, and must be obtained through Maintenance.

The engine oil system

Let us first emphasize that, according to the “Supplement”, the only approved oils are Shell EP

75W90 API GL-4 and Shell Spirax GSX 75W-80

The engine oil system is a wet oil sump system containing up to 6 litres. A wet sump system means

that the oil is stored in the engine’s casing rather than in a tank (in which latter case one talks about a

dry sump system). The oil level can be checked by means of a dipstick located on the upper center

nose cowling. It should not be less than 4.5 litres, as indicated by the level being between two red

markers at the extremity of the dipstick . The maximum engine oil consumption should not exceed 0.1

litres/hour.

The system is rather straightforward: its main line supplies the various engine parts with the

necessary engine driven supply pump, oil pressure sensor, oil filter and oil temperature sensor, the

used oil being then returned partly by gravity, partly via a so-called catch-tank and associated gear

pump, back into the sump. An additional oil line supplies the turbocharger, and also drains into the

catch-tank.

Downstream of the oil filter, a thermostat ensures that whenever the oil temperature is lower than

78°C, the oil streams directly to the engine and the turbocharger. If the temperature is between 78°C

and 94°C, the oil is partly directed to an oil cooler adjacent to the cooling fluid’s heat exchanger (see

below), then further through the normal path. Above 94°C, all of the oil goes through the oil cooler,

thus ensuring a maximum oil temperature of 140°C.

Note that, although the maximum oil pressure is normally 6 bar, when starting in cold weather

conditions, it is allowed to build up to 6.5 bar for up to 20 seconds. Assuming a low oil pressure

condition, this will activate the “OIL” warning on the original annunciator panel.

The gearbox oil system

This is also a wet sump system, the oil being used for lubrication and cooling of the gearbox, as well

as for the propeller’s constant speed unit. The gearbox oil is not the same as the engine oil: according

to the “Supplement”, the Shell EP 75W90 API GL-4 type is solely to be used.

The system contains only 1 litre. The oil level can be checked by means of a viewer located behind a

small panel at the left lower front side of the engine cowling.

Note:

Although the engine and gearbox oil pumps are said to be engine driven, in fact

they are one single unit, known as a combined system, driven by the gearbox.

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THE ELECTRICAL SYSTEM, THE FADEC & RELATED INSTRUMENTS, ENGINE MASTER

SWITCH

General

The operation of the electrical system is very much the same as prior to the engine retrofit, the most

important difference being the addition of the FADEC system. As the operation of the engine depends

largely on the proper operation of the FADEC, the important thing to be aware of is that the TAE 125-

1 engine, besides fuel, also needs electrical power to keep it running.

According to the “Supplement”, the alternator field is supplied by a 12V excitation battery, whose

secondary purpose it is to supply the FADEC (at least for some time) in case of failure of the main

battery. The complete battery arrangement, main battery and excitation battery, is located in the

fuselage, behind the baggage compartment.

Note that, unlike the main battery, the excitation battery is not recharged by the alternator.

Consequently, besides regular inspections by Maintenance, the excitation battery must be replaced

once every 12 months.

The master switch is a single battery switch controlling the main battery only, the alternator being

controlled by an adjacent circuit-breaker supposed to remain pushed in all the time. Selecting the

battery switch “ON” supplies all busses and their associated users, except the navigation aids which

require the selection of the avionics power switch. Neither does it power ALL of the FADEC

components, some of these being activated by the engine master switch (see below).

The FADEC

FADEC stands for Full Authority Digital Engine Control, i.e. the heart for the functioning of the TAE

125-01 engine. Just as is the case on gasoline power plants where the magneto system is dual, the

FADEC consists of two identical redundant halves labelled A and B or, to put it simply, two computers

operating independently, one being the “active” system the other being the “standby” system, ready

to take over automatically should the “active” fail. FADEC A is normally the active one. Both these

computers are located behind the right hand part of the instrument panel. As said earlier, the FADEC

system is designed to operate on a tension of 14V.

Each FADEC registers a total of 16 signals from sensors in the various parts of the engine. The

sensors are in communication with a total of 9 so-called actuators, i.e. the users of the various

signals, through 5 main control loops. These loops are activated partly by the main battery switch,

partly by the engine master switch.

As an example, let us consider the sensors related to the barometric pressure, the manifold air

pressure, the outside air temperature and the thrust lever’s potentiometer. All these signals allow the

FADEC to calculate the exact amount of fuel to be injected in the cylinders in order to obtain the

required power. Similarly, a propeller signal (sensor) allows the FADEC to select the most suitable

propeller blade angle (actuator). In other words, as the pilot must not be worried by fuel/air mixture

problems, there is no mixture control lever, and, as said before, there is no propeller lever either. In

fact, the pilot has no direct control on the engine: he orders a certain power setting through the

thrust lever and its associated potentiometer, the FADEC performs the required calculations and

executes.

Controller Area Network, CED, AED

The FADEC is fitted with a so-called Controller Area Network system, abbreviated “CAN”. The purpose

of the CAN system is to ensure fast and efficient communication between the various FADEC sensors

and actuators, thus improving the global efficiency of the electronic system. The CAN also allows a

laptop computer with suitable program to be connected to the FADEC. This feature is for maintenance

only, and allows the rapid detection and location of possible FADEC malfunctions. Incidentally, the

laptop computer also shows the total engine running time.

Versie oktober 07

It is also through the CAN system that the FADEC transmits information to two related instruments,

the CED 125 and the AED 125. The indications on these instruments occur through light emitting

diodes whose intensity may be adjusted by an adjacent additional rheostat.

a) CED stands for Compact Engine Display. It integrates all engine data which are to be

monitored during flight, namely the RPM, both in digits and range, the oil pressure(OP), the

oil temperature (OT), the coolant temperature (CT) and the gearbox temperature (GT), all in

range only, and finally the % of load both in digits and in range.

Range indication are colour coded green, amber and red. Any time a reading is in the amber

or red range, the “Engine Caution” warning light illuminates on the FADEC’s central warning

system and extinguishes only when the adjacent “CED Test/Ack” pushbutton is depressed

(see below).

b) AED stands for Auxiliary Engine Display. It displays the fuel temperature, the fuel tanks

contents and voltage.

FADEC’s central warning system

[HOP2]

The FADEC’s central warning system comprises a red “Engine Caution” annunciator and a common

“test/ack” pushbutton which can be used either for testing both instruments or to extinguish the light

if it is caused by a yellow or red warning showing on the CED.

A separate “GLOW” annunciator is located close to the Starter Key.

In addition, the central warning system includes two red warning lights, one for FADEC A and one for

FADEC B. Assuming that FADEC A, the active one, fails, its associated red warning light will flash, and

the system will normally switch over automatically to FADEC B. Should this not be the case, as made

evident by the engine’s abnormal behaviour, the switching from FADEC A to FADEC B can be done

manually by pulling the “Auto FADEC – Pull to Force B” breaker, adjacent to engine master switch.

Assuming that both these lights should flash simultaneously, this may be indicative that a fuel tank is

running dry (see fuel system above).

Assuming however that, although the fuel level status is satisfactory, both FADEC red warning lights

are flashing, according to the “Supplement”, this situation does not necessarily lead to an engine

failure but, even if the engine continues to run, the load display may not correspond to the current

value, and a total engine failure might be expected at any moment anyway.

The engine master switch, engine starting system

As mentioned earlier, because of its basic operating principle, no ignition system is required for diesel

engines. However, some engines are difficult to start when they are cold because the temperature of

the induction air at the end of the compression stroke is still too low to produce spontaneous ignition

and combustion. It is only once the engine is running that sufficient heat is produced to sustain

combustion.

This is particularly the case with IDI which requires induction air preheat assistance. This is achieved

by electrically heated glow plugs, one located in the combustion chamber of each cylinder, and which

momentarily produce a temperature close to 1000°C.

Although DI engines are less prone to starting problems, the TAE 125-1 is fitted with a similar glow

plug system to improve the starting behaviour when the engine is cold, particularly in combination

with low outside air temperatures. On the TAE 125-1, the glow plugs are FADEC-controlled, as are the

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fuel injectors in each cylinder, both systems being electrically supplied when the engine master switch

is “ON”.

The engine starting procedure is extremely simple. With the main battery switched on, the selection of

the engine master switch to “ON” causes the glow plugs to heat up, which is indicated by the “GLOW”

warning light momentarily illuminating. It also causes the fuel injectors to open and allow fuel under

pressure stored in the common rail to be injected in the cylinders, the whole operation being FADEC

controlled. As soon as the “GLOW” warning light extinguishes, and with the thrust lever in full idle

position, engine starting may be initiated by turning the starter key.

Small detail: the engine’s hobbsmeter (hourmeter) starts “counting” as soon as the engine master

switch is selected to “ON”, whether the engine is running or not. Switching the engine master switch

to “OFF” causes the engine to shut down.

[HOP3]

CAUTION: Selecting either the battery switch or pulling the alternator circuit-breaker to

“OFF” will not cause the running engine to stop, at least not immediately (see below).

However, if both battery and alternator are switched off, as the FADEC is no

longer electrically supplied, the engine will stop at once. If the alternator fails,

electrical power will be provided by the battery only. The time the engine can run on

battery alone will depend on total electrical consumption supported by the battery.

ENGINE COOLING AND CABIN HEATING SYSTEMS

Both these systems are closely related. As was mentioned earlier, the engine uses liquid coolant

instead of being air-cooled. One advantage of the liquid cooling system is that shock cooling during

descent is eliminated. The coolant is stored in a tank within the engine compartment, and is a fiftyfifty

mixture of water and BASF Glysantin Protect Plus/G48, again a product which is only available

through Maintenance.

Prior to start engine, the pilot must check the coolant’s level. This is done by means of a yellow

“COOLANT LEVEL” warning light. When the battery switch is selected to “ON”, it is imperative to verify

that the warning light initially illuminates (mostly very shortly) then extinguishes. Assuming that the

light remains illuminated, the coolant level is too low and engine starting is prohibited. Note also that

engine starting is not allowed if the coolant temperature happens to be lower than -30°C. Incidentally,

the same limit is also applicable to the engine oil and gearbox temperatures.

Engine cooling circuit

The coolant leaves the tank and is pumped into the engine where it evidently picks up heat. Upon

exiting the engine, the coolant is directed to a three-way thermostat of which one exit is unregulated

and relates to the cabin heating system (see below). The two other exits regulate the coolant flow

between a so-called short circuit and/or a large circuit (also referred to as “external circuit”),

depending on the coolant’s temperature:

a) Assuming that the coolant’s temperature is less than 84°C, the coolant circulates through the short

circuit which directs it immediately back to the engine via the pump.

b) Assuming that the coolant’s temperature is between 84°C and 94°C, the coolant is caused to flow

partly through the small circuit, partly through the large circuit. This latter circuit includes a heat

exchanger (radiator) located on the left side of the engine, where the fluid is cooled by outside air

coming from the left upper air intake on the front part of the cowling. This heat exchanger is divided

in two parts, one serving the coolant’s fluid cooling, the other serving the engine oil cooling (see

engine oil system). Upon exiting the heat exchanger, the coolant fluid is directed partly back to the

tank, partly back to the engine.

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c) Assuming that the coolant’s temperature is more than 94°C, the short circuit is completely

bypassed and all of the fluid is directed through the large circuit, thus ensuring a maximum coolant

temperature of 105°C.

Cabin heating and defrosting system

Except for the fact that when the cabin heating is operative, windshield defrosting operates as well.

Outside air is still used, but it is now heated by contact with the hot coolant fluid exiting the engine

through the third non-regulated thermostat’s outlet in a second heat exchanger. The air inlet for this

heat exchanger is located in the lower part of the front engine cowling.

This heat exchanger is fitted with a valve which is controlled by a knob on the instrument panel: the

so-called cabin heat shutoff (unfortunately simply labelled “CABIN HEAT”) which can be selected in

open or closed position:

a) In the open position (knob pulled out), the valve in the heat exchanger directs the heated outside

air to a second valve located in the engine firewall. This latter valve is controlled by a second knob on

the instrument panel (also labelled “CABIN HEAT”!!! find it on the right hand side of the first one,

immediately above the “CABIN AIR” control) and admits or prevents the heated outside air to enter in

the cabin (exactly as was the case in the original system). When this second knob is pushed in, the

outside heated air is dispersed in the engine compartment.

b) In the closed position (knob pushed in), the valve in the heat exchanger pre- vents the outside air

to flow to the firewall, also dispersing it in the engine compartment. In other words, when the cabin

heat shutoff knob is closed, the usual cabin heat knob has no effect. The open position (knob pulled

out) is the normal position during flight.

VACUUM SYSTEM

Only one vacuum pump remains available since the installation of the TAE 125-1 engine.

EMERGENCIES

Section 3 of the “Supplement” covers the TAE 125-1 related emergencies.

In addition to Section 3 please find below some helpful hints:

01.- Assuming an engine failure in flight, selecting the thrust lever in middle position and cycling the

engine master switch “OFF” then “ON” may help to restart the engine. In addition, no restart should

be attempted above 13000 ft.

02.- Considering the propeller stopped case, the best is to consider that, if the propeller stops at more

than 70 KIAS, the engine or propeller is blocked and refrain from using the starter.

03.- Considering the FADEC malfunctions in flight (pages 3-6 and 3-7 of the “Supplement”) three

cases are considered: (a) one FADEC light is flashing, (b) both FADEC lights are flashing and (c)

abnormal engine behaviour. Regarding this latter item, the text says (page 3-5): “If the engine acts

abnormally during flight and the system does not automatically switch to the B-FADEC, it is possible to

switch the B-FADEC manually”. The question is: how can the pilot know that B FADEC has not

automatically replaced A FADEC? Probably by the fact that, following the illumination of A FADEC

warning light, the engine shows “abnormal behaviour”.

If we consider the “BOTH FADEC WARNING LIGHTS ARE FLASHING” case, if this happens with

satisfactory fuel contents, one may believe that it may be due to the fact that B FADEC has not

automatically taken over, and that switching manually to B FADEC might restore normal engine

operation.

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AIRCRAFT PERFORMANCES & LIMITATIONS

The “Supplement” contains charts for takeoff distance, time fuel and distance to climb, cruise

performance including range and endurance… but for some reason, no short field landing distance.

Regarding the takeoff distance charts (page 5-2 of the “Supplement”), two conditions are considered:

takeoff at maximum allowable weight 980 kg, and at 880 kg. Note that TAE considers 1 litre of fuel for

engine start, taxi and take-off.

With regard to range and endurance, the values are based on 109 litres on departure.

The aircraft is certified for both Normal and Utility categories.

Maximum allowable altitude is 16500 ft.

WEIGHT & BALANCE

Remember that diesel and JET FUEL are heavier than AVGAS and they carry more energy

per volume. Because the fuel in the Robin series is in an aft location, fuel consumption shifts the CG

forward. The DR400/135CDI delivers greater range and, at altitude, greater speed, than

AVGASpowered Robin of equivalent sea-level power ratings, for a given volume of fuel.

Normal category

Maximum ramp weight: 980 kg

Maximum takeoff weight: 980 kg

Maximum landing weight: 980 kg

Utility category:

Maximum ramp weight: 910 kg

Maximum takeoff weight: 910 kg

Maximum landing weight: 910 kg

Consequently, assuming two occupants of 80 kg each + 10 kg of baggage (flight cases, etc…) + fuel

up to 110 litres, we have:

600 + 160 + 10 + 89 = 859 kg ramp weight, 858 kg takeoff weight

Needless to say that a third person on board would significantly reduce the allowable fuel load. As for

operations in utility category, it seems that only two persons can be on board.

Note also that the “Supplement” includes only a “LOAD MOMENT” graph. This document is to be used

together with a copy issued from the original POH for the “LOADED AIRPLANE MOMENT/1000” and

“AIRPLANE C.G. LOCATION” graphs. These documents are those which must be used for load &

balance calculations

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Robin DR400/140B Supplementary Information

Brand: Robin

Model: DR400/140B

Category: Engine

Type: Supplementary Information

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Robin DR400/140B Supplementary Information

Robin DR400/140B Supplementary Information

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