@Arne unfortunately this RED engine is way too heavy for the intended use.
I just watched a video showing an Extra 500 (lightweight power plant) taking off and landing.
It is obvious that the Extra 400/500 airframe was designed for this turbine engine, and the piston powered variant was only meant as a “make do” first step with a common airframe and CG as a cost compromise.
Furthermore, avionics upgrades on the Extra 400 remove 20 Kg of old stuff from the tail, adding to the problem.
The Extra 400 cannot rotate as slow as the 500 video shows.
I find it unstable and rather difficult to handle under 80 knots: fighting the engine which is pushing the nose down and the T-tail elevator is at a disadvantage.
The 400 with upgraded avionics is so nose heavy that one would bust the forward CG limit with 2 big pilots and no PAX.
I have also analyzed how the elevator is set at cruise speed. It is definitely applying a lot of downforce, again exposing the imbalance. It is not even possible to bring the yoke to “neutral” – the plane takes a sharp nose dive before getting there.
So back to the piston engine: the ideal candidate would weigh 100 lbs less, but there is no such thing available in the real world. Despite being a dreamer, I am not a fan of betting on engines that will “soon” be available such as Adept etc…
So I still see the TSIOL 550 as the best best for an experimental piston solution, considering that it is possible to shave off some weight as follows:
- Smaller turbocharger (the factory one is oversized – it delivers full rated MP at the certified ceiling )
- Electronic ignition (mags out)
- Minus one vacuum pump (two were justified for fault tolerance with vacuum powered instrumentation)
- Lightweight starter – this combines well with EI to avoid reliability issues
- Smaller alternators (modern avionics and LED lighting mean reduced power needs)
Here more radical ideas in an experimental context:
- Move coolant and oil radiators to the back (P51 style). This would add long and heavy fluid lines but, there is room for them and one could probably recoup the weight penalty by using smaller radiators in the uncompromised underbelly air ducting context (higher efficiency on the air side). Also, a simpler cowl with less openings/reinforcements will weigh less.
- install a mini canard (!) providing up to 100 lbs of lift at takeoff and landing AOA.
Forgive me for being such a dreamer. I just can’t help trying to find the way to do justice to this aerodynamic work of art. If you have the opportunity, take a close look at the wing and flaps. Beautifully curved profile and genius engineering still setting the bar 25 years after it was developed…
That’s the new bird. (The white one in the back) Have not flown it yet.
WOW – which of the two will be the spare parts donor?
Nice photos and it saddens me that this plane is up for sale.
The owner is a dear friend, CFI and A&P who always took the time to document and share issues and fixes for the benefit of our group.
He won’t even claim any merit, but I think he pampered and improved his plane like only an A&P can, finding documentation and sources for spare parts and overhaul shops that I for one could not locate… People like himare needed to « finish the project » and provide much needed help:
When one of us was in need, including yous truly, he would take time off his busy life to help.
I fear that we will miss his contribution once his E400 finds a new home.
@Flyingfish. Had you evaluated https://www.ac-aero.com/hawk/?
Yes I have looked at it.
It seems a bit on the miraculous side to me. I have learnt to be skeptical about claimed quantum leaps. Also the online docs show “Higgs Diesel” all over while this supposedly is no diesel.
Maybe someone can comment on actual availability and real world applications?
@Flyingfish thanks for reply.
@Bad_mauro got me thinking. ;-)
AC aero also offer a “stroker” version of the Lycoming 540 with 415 HP.
What if we went normally aspirated then? Could this be the better solution to a turbine conversion in Euro skies?
Some math:
Switching to this engine (6 cylinder, water cooled, no turbo, no intercooler, no wastegate) would save 40 Kg (88 lbs) off the nose, exactly what is needed to push the CG back to where it belongs.
This plus lower cooling drag compute to 3 KTAS extra airspeed which was added to the below .
415 HP normally aspirated took on 350 turbo horses in a spreadsheet and yielded this:
Nicer take-off handling and massively better climb performance up to 10’000 ft, especially on hot days.
Better CG should also allow “by the book” approaches and slightly improve landing performance.
Cruise speed below FL 100 increases by up to 25 knots, allowing 185-190 knot cruise at ANY altitude from SL to FL180.
For my mission profile, mostly 400 NM legs east to west and back, this is a big deal: headwinds at altitude frequently force us to stay low at 165-170 KTAS.
Climb performance is degraded above FL100 and becomes critical above FL180.
This is the most annoying bit: punching through icing layers in the climb would be unreasonable above FL 120.
The breakeven point for “time to climb” is FL150: It would take 15 minutes from SL in both cases
Does anyone have a ballpark for additional manifold pressure from a well designed unfiltered RAM air intake?
Weight reductions in aircraft and women (did I really write this? RIP) always start a virtuous circle, enabling more of the same from the tail compartment and main gear.
This means that useful load will increase. A very welcome bonus.
What you say ?
How would you solve the pressurisation problem with no turbo?
Pressurization is part of a broader concept, hence the long answer :-)
The tail compartment, behind the pressure vessel is very roomy and contains an “old style” AC system, the aircraft battery and avionics.
Given that the aircraft would be Experimental, the following is possible:
1) Replace conventional AC compressor with a modern, lightweight, higher efficiency unit. New technology with much lower weight and power draw is available from the EV industry.
2) install an electrical compressor for pressurization
3) install a digital climate control system
Another option is keeping one of the 2 vacuum pumps and allocating it to cabin pressurization, but I am not sure it would be enough.
