Extra 400 Wiki



Welcome to the Extra 400 Wiki
This is the platform for consolidating and sharing our knowledge about the Extra 400 and 500 aircraft.

We are a closed community, meaning that we do not intend to open this wiki to the public.

The site is targeted at owners, operators, pilots as well as technical people working on these aircraft. It is also open to select suppliers of parts and services.

DISCLAIMER: the editors of this site are not the type certificate owners but merely interested parties that want to share information and knowledge informally and for their mutual benefit. USE THIS INFORMATION AT YOUR OWN DISCRETION AND RISK AND APPLY OWN JUDGEMENT. NO LIABILITY IS ACCEPTED BY ANY OF THE EDITORS FOR ANY CONSEQUENCES OF USING THIS SITE. IF YOU DISAGREE WITH THIS YOU MAY NOT ACCESS THIS WIKI.

What is the Extra 400?
This aircraft is arguably the highest evolutionary step in single engine piston aircraft.

Developed in Germany and Holland in the 1990's, the Extra 400 is an all carbon-fiber composite pressurized six-seater travelling machine.

Although its layout looks similar to that of a Cessna P210, its only direct competitor really is the Piper Mailbu/Mirage family.

The aerodynamic design of the Extra 400, the immense strength of its carbon structure, its roomy cabin that rivals that of entry level bizjets and its general level of refinement make it a far superior aircraft to the Piper PA46 Malibu/Mirage.

Healthy E400s climb much better than the PA46 (by at least 50%) and they are also slightly faster (5-10 knots).

This is probably why the few available samples of this very rare animal attract considerable interest from all over the world - not to mention the flock of pilots around you as soon as you taxi to the ramp!

Of course, with such a low number of aircraft built, the Extra 400 design cannot be considered mature. There are some quirks and issues that need to be fully understood and accepted by operators and the aircraft should not be put into the hands of inexperienced pilots.

But when fully harnessed, an Extra 400 will give you flying pleasure, utility and performance in a combination that is out of reach of any other SEP.

Origins and history
We have approached prof. Egbert Torenbeek from the Technical University of Delft.

Prof. Torenbeek is the lead designer of the Extra 400 airframe and he is an invaluable source of knowledge. He generously offered to share documents and information about the design phase that we intend to publish here.

It is noteworthy that Prof. Torenbeek has been honored by the AIAA Aircraft Design Award for his lifetime work, of which the design of the Extra 400 is a major milestone.

Should you be flying an Extra 400?


The Extra 400 is a complex, high performance pressurized aircraft.

While its performance and features make it extremely enticing, you as the pilot need to be fully aware of the fact that it is a demanding aircraft and certainly a maintenance challenge. If you intend to fly an Extra 400, you should be: If your skills cover all of the above, you should be OK flying the Extra 400.
 * experienced and current enough ( 500 hours total and 50 hours latest year as a minimum)
 * a very good "stick and rudder" pilot
 * an experienced IFR pilot (at least 100 hours)
 * familiar with the operation of engines in the 300 HP power range.
 * technically interested with above average understanding of aircraft and engine operations.
 * willing to accept that you may very well be the first one to be confronted with a new problem

Keep in mind that this is an orphaned aircraft which was not completely developed at the time production stopped. As a result, there are some quirks that must be mastered. Do not expect to drop the aircraft somewhere and say "fix it"...

Thorough transition training is necessary and you are encouraged not to skimp on recurring training. Again, this is no ordinary aircraft and you may well encounter some new and challenging situation.

Stay alert, practice your emergency procedures with a qualified instructor and have your checklists handy.

Advice on basic operations
Climb like a homesick angel?

If everything works fine and atmospheric conditions are near ISA, you should be able to climb at 1'000 ft/min to 20'000 ft with the following settings:

37.5 inches and 2500 RPM. Fuel Flow: 125-130 liters per hour (33 to 34.5 GPH). TIT around 1500 F.

At MTOW, expect IAS between 115 and 120 knots.

If any of the above parameters is not right, have your engine checked. In particular fuel flow is absolutely essential, but mag timing may also be playing a role.

If coolant temps get out of control:

1. Check your coolant radiator for damage to the fins that can block airflow

2. Make sure that the transition between the inlet lip and the coolant radiator air duct is SEALED. The default setup uses four separate pieces of baffle material. Replace with a single continuous baffle part and seal it.

3. There is a gap at the top of the air duct between this duct and the top of the radiator. Hard to see, use a flashlight... This can be sealed as follows: install a sealing flap in the airbox and cut out clearance for the radiator mounting bolts. Seal the box from the outside using a line of RTV. (The flap will prevent the RTV Broken baffle material or steps in the shape will cause major degradation of the cooling performance.

Recent experiments with improved airflow an airtightness to the coolant radiator have delivered very encouraging results on a moderately hot day (ISA+15 C).

The aircraft took off at 50 Kg (100 lbs) below MTOW and climbed at 88% power, 120 KIAS, 1'000 ft/min until FL150.

Coolant temps were slowly increasing until FL100 and then stabilized. At FL150, Inlet Air Temperature reached 130 F and coolant temps started to increase again. Reducing MP to 36.5 inches and climb rate to 800 fpm took care of this and the aircraft reached FL190 without overheating.

Whenever temperatures exceed ISA+15, one should expect challenging thermal management.

The following has helped:

Keep RPM as low as possible until take off.

When waiting for clearance, point the nose into the wind.

If runway length allows, reduce take-off manifold pressure to 37.5 inches,

Rotate late and keep airspeed higher during initial climb to increase air flow.

If necessary, level off, reduce power and let the coolant temp recover before initiating the climb.

During the climb, keep 120 KIAS, watch the trend of coolant temp and proactively reduce climb rate and reduce MP to stop the creep.

The above will result in reduced take-off and climb power. Add the effect of high density on the airframe and it becomes obvious that managing take-off weight becomes very relevant.

Economy Cruise settings

SN 03 had the so called "balanced flow injectors" from Continental installed. It nevertheless failed the GAMI test so that GAMI injectors were subsequently ordered and installed. GAMI knew exactly about the issue.

Unfortunately, it has not been possible to run LOP without TIT exceeding the 1650 F limit.

As a result, SN03 is not being operated Lean of Peak. Feedback from other aircraft shows a similar situation.

As an alternative, the following economy cruise settings have been found to provide a great performance/fuel flow combination while keeping TIT in check: Smooth landings
 * MP: around 29 inches (results from the fuel flow setting that achieves 1650 F TIT)
 * RPM: 2250 (it seems the "b" blade Scimitar prop has an efficiency sweet spot at 2250 RPM)
 * Fuel flow: 74 liters per hour (19 GPH)
 * TIT: 1650 F
 * Airspeed at FL200 / ISA day/MTOW: 190 KTAS

Approach at MTOW: 80-82 KIAS, power 17 inches. Less if lighter.

In short final, trim nose up to slightly more than the take-off setting.

You'll know you have the right trim setting when minimal force is required to negotiate the final seconds of the touchdown. Yes it is possible to grease it!

Oil top-off - not!

Fill up to 9 Quarts and let the level drop down to 8 before refilling This will keep oil consumption at an optimum level and will avoid a dirty belly.

This will keep oil consumption pleasantly low and cause less mess under the belly.

Known issues and precautions
Preventing leaks from the hydraulics of the gear.

The landing gear hydraulic actuators are exposed to the elements. On the left side, the engine exhaust sprays corrosive deposits on the exposed hydraulic cylinders.

After landing you'll see a black ring of dirt on the shock absorber cylinder which has been pushed up by the ... O-rings.

It is advisable to use WD40 as a solvent and wipe off the dirt as frequently as possible. Spray WD40 again after that to provide corrosion protection.

This way, the amount of dirt accumulating on the O-ring (and likely to cause scratches, cuts, leaks) will be minimized.

And use every opportunity to top off the greasing pins.

One wing low on the ground

There is no excuse for this. When the gas shock absorbers are properly filled to 57 bar / 827 psi, the plane sits and taxis level. Period!

The gear structure may not look "tired". The articulated arms should draw a perfect straight line. All it takes is 57 bar / 827 psi on both sides.

Understanding CDT and IAT temperature

The TSIOL 550C engine is outfitted with a single turbocharger that generates manifold pressures of around 40 inches of mercury at full boost. While the turbo is powerful enough to produce this MP at the aircraft's service ceiling, the AFM states a restriction above 20'000 ft that is the telltale of an issue we need to understand and fully account for when operating the aircraft.

The boost from the turbo comes at the price of a large increase in the temperature of the compressed air.

This temperature is referred to as "CDT" or Compressor Discharge Temperature. The higher we fly, the hotter the CDT gets.

This is due to the fact that the outside air gets less dense at a rate that is higher that the decay of temperature, forcing the turbo to work harder and harder, which generates additional heat.

This very hot air gets cooled by the intercooler before being fed into the engine inlet. The post intercooler air temperature is called IAT for Inlet Air Temperature.

The intercooler works best when outside air is coldest AND most dense.

So if the air is very cold and not dense, it may cool less efficiently than if the air is denser and a bit warmer.

Therefore, counterintuitively, it is not so that the intercooler works best at FL250...

Now we have the explanation of the AFM restriction on MP above FL200: it is the "double whammy" of the turbo working harder and the intercooler's efficiency affected by low density air. The result is an increase of the inlet air temperature (aka IAT) which reduces engine efficiency and detonation margin and increases heat generation.

How warm does the inlet air (IAT) end up being? This is a key question that affects the performance of our engine in a profound way. Experiments and observation with a suitably equipped aircraft show that as soon as IAT reaches 130 F, thermal management becomes difficult. A respected F1 and aircraft motorist suggested 130F as the limit.

IAT is affected by three parameters of which we can influence only the first two:

- CDT (this is how hot the air is before entering the intercooler)

- Intercooler efficiency

- Outside air temperature

CDT is influenced by engine settings and to a large extent by the amount of work the turbo has to do to achieve the desired Manifold Pressure.

We can significantly improve CDT by avoiding unnecessary work by the turbo. The turbo needs to make up for any leaks that occur in these three areas:

- induction

- exhaust

- cabin pressurization

So if your engine is not able to produce the climb and/or cruise performance that other operators are seeing without overheating, have it checked for such leaks.

After learning about the above, the owner of SN003 decided to install temperature probes for both CDT and IAT in order to understand what is going on, detect issues and avoid operating the engine at too high IATs which will inevitably cause overheating and related damage. The (certified) probes were installed on the intercooler itself and connected to the engine monitor for data logging.

For a given Manifold Pressure setting we can influence CDT by increasing fuel flow to reduce EGT and TIT.

After several flights and some number crunching it turns out that intercooler efficiency is between 43% and 50% - mediocre values - both in climb and cruise conditions.

The recommendation is to make sure that the best possible seal is made between the intercooler and its air box behind the NACA inlet to maximize intercooler efficiency. This interface was not fully developed and requires RTV -literally- as a stop gap.

Turbine Inlet Temperature limitations

The POH states a redline limit of 1750 F. This is considered excessive by several knowledgeable people and consensus is that 1650F should be used instead.

It is important to note that TIT probe readings may be inaccurate. Ideally, we should have our probe calibrated, but this requires specialized equipment.

Insertion depth is also critical: 19mm is the correct value. Incorrect insertion depth will cause bad readings of TIT.

Turbo wastegate sticking
Power loss during the climb can be caused by a wastegate sticking open. Power can be recovered at a lower altitude and it may be that the wastegate unsticks then. Make sure to properly lubricate the wastegate and have its smooth actuation verified on a regular basis.

Turbo to intercooler duct disconnect
At least three occurrences of this incident have been identified. The duct that connects the turbo to the intercooler comes lose in flight. Depending upon altitude at the time of the event, this is perceived as a more or less explosive engine stoppage with subsequent loss of cabin pressurization.

Depending upon altitude the engine may completely stop producing power due to excessively rich mixture. Propeller windmills.

The cause of this is that it is extremely difficult to reassemble the lower cowling to the aircraft while simultaneously slotting the intercooler into its lower supporting rail. The resulting tension in the short ducting between turbo and intercooler can force the silicon duct out of the metal end parts. Power loss at altitude in VMC
 * It is advisable to carefully watch this issue when re-assembling.
 * Pilots should always have emergency oxygen ready for use when operating above FL120.
 * In the case of SN03, the incident happened at FL190. An emergency descent to FL100 was conducted and the engine restarted more or less by itself at this altitude.
 * If this happens to you, descending to a lower altitude (around 10'000) will allow an engine restart. Use checklist to do so. You will have less power but OK for landing.

FL 190. The engine started sputtering and lost power. Emergency landing. Cause was determined to be engine air filter icing. This occurred in VMC, 15 minutes after leaving the wet clouds. The air filter must have been soaked with humidity...

Hydraulic pump circuit breaker failing
The 50 amp circuit breaker that protects the hydraulic pump is subjected to high currents, sometimes even more than its rated break point.

The part tends to wear and eventually fail. Two known incidents. When this happens in flight, the landing gear extends, making the aircraft extremely draggy. Keep airspeed under Vle (140 KIAS) and proactively apply enough power to limp home while watching engine temperatures as the aircraft is now much slower and less cooling is available while relatively high power is necessary.

Preemptive replacement is a wise move, especially if you have been experiencing trouble that causes the pump to run frequently or for a long time.

Leaky Fuel Vents
This is quite a common occurence.

The factory has made two successive designs of the fuel tank venting. Some of the early aircraft have been modified. Both systems are depicted in the AMM.

The fuel vent that is frequently causing trouble is located around half of each wing, on the trailing edge. It is installed about in the middle of the tank’s height. This means that it is submerged when the tank is full.

The vent contains a mechanical sealing system that uses a hinged 90 degree lever with a piece of solid foam bonded to the arm of the hinge that applies pressure on the rubber seal when the foam part is floating.

Leaks can happen for the usual reasons (foreign matter preventing a clean seal, cracked rubber) and also when the mechanical sealing system is damaged.

This system can be replaced (one man-day of labour) but parts availability in the field is uncertain. The Extra factory probably still has them though.

In one instance, the leak stopped without any intervention and we are guessing the cause of the leak was foreign matter that got drained away.

So it may be worthwhile cleaning the part before declaring it unserviceable.

Pressurization issues
The pressurization system is complex. This is inherent to the piston engine which requires deriving the necessary cabin pressure from the turbocharging system. In this paragraph, we would like to report real world issues and their fixes as opposed to describing the system (this description is available in the AMM and AFM).

The SCEET ducting inside the engine compartment is very complex and prone to developing leaks because it must be partly dismantled every time the lower cowl is removed.

The cabin door has a seal that is supposed to inflate under the pressure differential in flight. The seal may be damaged when the doors are inadvertently closed with their sealing pins in the extended position. Replacement seals are available from Extra but their are not as good as the original ones which have carefully contoured curves with embedded stiffeners in all four corners, so don't hurry and replace un old seal unless it is really damaged beyond repair.

The two outflow valves which are located in the back of the pressure vessel are reasonably accessible behind the upper panel of the baggage compartment. They tend to collect dust which means that they can lose their airtightness and can cause random excursions of cabin pressure as they do their work. Preventive cleaning is advisable. It is also generally a good idea to thoroughly vacuum clean this area of the pressure vessel to minimize the risk of small debris getting sucked into the valves

Also accessible behind this panel are the pass-through tubes for the flight control cables that go to the tail. These tubes are "stuffed" with rubber-like seals around the the steel cables. The effect of friction there can be seen in the form of rubber material embedded in the cables. It is probably wise to replace the rubber seals on a regular basis.

RFI filters catching fire
At least three occurrences of this are known. The RFI filters located on the top front of the engine are being used at their maximum design current limit of 100 A and are not mounted on a heat sink as the manufacturer recommends. They overheat and can fail and catch fire. Given proximity of the main fuel line this is a severe risk. These filters only filter out noise in the GPS frequency band so they are not very useful.

One aircraft with upgraded avionics is now flying with the filters suppressed and no adverse effects. If you decide to keep the filters, replace them as you deem appropriate and have a heat sink fitted in compliance with the manufacturer's instructions.

Coolant leaks

There is a potential fatigue issue on the aluminum tubing of the check valve which is mounted vertically between the top and bottom of the reservoir (it passes through a hole in the reservoir mounting bracket).

Recommendation: inspect and replace this tubing ( it is easily remanufactured) as a preemptive measure if you have no evidence that it has been done recently. Upon reassembly - take appropriate measures to prevent chafing.

The plumbing of the liquid cooling system is vulnerable to chafing. It is pressurized so that even a small puncture will cause a jet of coolant and a total loss of pressure which will make the coolant boil away.

One owner reported such a failure and a subsequent emergency landing.

Recommendations:
 * 1) At every occasion thoroughly inspect all cooling tubing for chafing.
 * 2) Make pressure tests on a regular basis to detect coolant pressure loss before it causes catastrophic overheat. For this purpose, pressurize the coolant circuit using a regular air source and check that it does not lose all pressure overnight.
 * 3) Update: courtesy of Ian Mc Kenzie. After working on the coolant circuit, this simple test detects any remaining air bubbles. Close the filler cap and note coolant level. Pressurize the circuit (by injecting shop air). If the coolant level decreases there is an air pocket somewhere that has not been purged.
 * 4) Remove and inspect the coolant reservoir at annual. The gasket at the bottom of the coolant reservoir can leak. A crack can develop on the top mounting flange where it attaches to the engine if the shims are not correct and there is tension in the assembly.

Performance reports
In this section, we would like to see data points presented in an honest and factual way. This is not about boasting. It is intended to give reference points and help in decision making and troubleshooting. The data is presented as a table to make comparisons easier

List of aircraft
The Extra factory reportedly built 26 aircraft before shutting down production. Four aircraft have been dismantled or accidentally lost. These are
 * SN 01 - factory prototype . There are photos showing its airframe being used in ultimate load testing
 * SN 02 - crashed just after delivery in Germany with one casualty. Accident report in German here.
 * SN 08 - emergency landed on water in Norway following an engine fire. No casualties. aircraft wreck has been offered for sale for some time and then vanished.
 * SN 10 - crashed in Oklahoma after take-off with 6 casualties.

List of serial numbers and registration history:

List of knowledgeable companies / Individuals
It seems that everyone assumes that the Extra factory no longer touch these aircraft. Not true.

They are quite happy to perform maintenance and repairs and certainly there is a considerable amount if knowledge and ... spare parts on hand.

In the UK: Eagle aero Engineering in Lydd airport. James Giller, james@eagleaero.co.uk

In France: alsace Air Maintenance in Colmar (LFGA) airport. Bruno Maire, alsace.airmaintenance@orange.fr

Repair of Moritz Engine Instruments: Radiant Power Corp. in Florida

☀https://www.rpcaero.com/product-families/instruments-sensors/flight-deck-instruments/

Overhaul of fuel pump, fuel metering specialist Great Planes www.gpfmtulsa.com

Overhaul of vacuum and pressure manifolds and valves: Quality Aircraft Accessories

☀https://www.qaa.com/products/aircraft-pneumatic-systems/aircraft-vacuum-manifolds

Hydraulic Pump runs permanently
Hydraulic Pump is not stopping or is restarting despite the absence of leak findings.

This can be due to a wrong setting of the pressure limit switch.

If the pressure limit switch is set to close at too high a pressure and the pump is unable to provide such pressure, the pump will run permanently.

The pump may be able to provide sufficient pressure during ground testing using an APU but not during flight operations at lower voltage.

Parts sourcing
Oil radiator

The oil radiator was manufactured by Behr in Germany and is out of production and out of stock at Extra.

Coolant radiator

Also out of stock. Two owners have sent their old parts for refurbishment to serve as spares.

Coolant tank

Out of stock. One owner has sent his old one for refurbishment to serve as spare.

High Capacity Coolant Radiator
(courtesy of Anthony Biddulph)

It appears that the original radiators fitted in the E400 aircraft were designed for automotive use and subsequently adapted for the aircraft. Experience of many users seems to be that this unit is capable of allowing the engine to operate without any cooling concerns only when functioning optimally.

Over time, fins get deformed by rain and insect strikes and performance starts to decrease.

N400YY by 2017 was difficult to fly within safe engine parameters. Climbs were often interrupted to allow air assisted cooling and climb rate was reduced. It was not possible to climb without the coolant temperature getting well into the yellow arc and with the oil also running dangerously high. On one flight in Summer 2018, the coolant stayed about 220 in the entire cruise of 3 hours. At this point the aircraft was grounded.

A decision was made to have the radiator sent to Pacific Oil Coolers in LA for refurbishment. After they had assessed the unit they suggested that with 2019 levels of technology, they could build a better unit and we commissioned them to do so. The replacement unit was fitted and took 9 liters of fluid vs. 7 liters on the old unit. Since it was fitted, the performance has improved massively. Coolant is now only mid green arc during climb and drops down to the white arc in the cruise. Oil temperatures always seem far more under control.

In essence, we no longer worry about rate of climb and operating the aircraft has become far less stressful!

The PAC radiator is longer than the factory unit by about 2 inches (5 cm). This still fits in the standard lower cowling except for a minor modification to accommodate the drain plug.

Extended exhaust
Early production aircraft had a very short exhaust tube.

More recent aircraft have a small extension (about 1 inch / 3 cm) added to reduce staining.

Some owners have had this extended even further and reported that it cured the staining issue.

Scimitar blade propeller
For N-reg aircraft there exists a Form 337 modification for the propeller to use "b" shaped blades from MT. These seem to provide a significant performance boost ( 5 knots in economy cruise and better climb). We should verify this by collecting performance data points from planes with the a and b type blades. The new blades can also be ordered with an extended metal leading edge protection. This is well worth the (big) expense as it eliminates a weakness of the MT blades.

Cabin Heat issues
No matter what position the Cabin Heat Bowden Cable button is set at, cabin air remains unpleasantly cool in winter. This issue has been investigated using a temperature data logger. The pressurized air coming from the sonic venturi has a temperature of 70 to 130 degrees F or 21 to 54 C. In cruise, expect about 75 F...

The cabin heating mixer and its associated ducting are located in an area of the cowling where temperatures are below freezing in cruise. As a result, the air that flows into the cabin is cooled to a point that the heater settings make no difference.

Furthermore, ducts 5 and 6 are routed close to the right hand exhaust manifold. The SCEET tubing would not survive for very long if exposed to the 1500+ degrees F of a potential exhaust leak. Unfortunately, such leaks do happen and we therefore have a potentially dangerous situation here. Similarly, duct 1 crosses from the LH side to the RH side behind the engine. This one can fortunately be routed away from the engine exhaust tubes.

It seems wise to wrap the exposed ducts 1,5,6 in adequate heat shield material.

The illustration below (click for full display) shows the factory setup during reassembly.

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T-Tail in the sunset. Photo by Timo S.



