AIRBUS RACER / Clean Sky2 LifeRCraft Demonstrator

[yasotay]

Unless Sikorsky can make the X-2 a viable civil rotorcraft, I think the X3 technology will do very well in the United States, especially with the oil and gas and emergency service segments.

 

[VTOLicious]

Any connection to AIRBUS? https://www.secretprojects.co.uk/th...utonomic-compound-to-exceed-rotorcraft.35604/

 

[TomcatViP]

K-RACER: An acronym for Kawasaki Researching Autonomic Compound to Exceed Rotorcraft.

Doesn't seems so.

Notice the straight shaft.

 

[VTOLicious]

K-RACER: An acronym for Kawasaki Researching Autonomic Compound to Exceed Rotorcraft.

Doesn't seems so.

Notice the straight shaft.

Shaft straight or not. I would think Airbus has patented this kind of compound helo configuration.

 

[TomS]

K-RACER: An acronym for Kawasaki Researching Autonomic Compound to Exceed Rotorcraft.

Doesn't seems so.

Notice the straight shaft.

Shaft straight or not. I would think Airbus has patented this kind of compound helo configuration.

The general arrangement of top rotor and two props is hardly original to Airbus. See the Fairey Gyrodyne, for example.

 

[TomcatViP]

Great example. I am also thinking at Ryan, Hiller...

 

[VTOLicious]

Indeed! ...However, I recall to have seen an Airbus patent somewhere. But I don't remember exactly the claims.

 

[TomS]

Indeed! ...However, I recall to have seen an Airbus patent somewhere. But I don't remember exactly the claims.

OH, I'm sure they have patented some specific implementation, and might well have made some overbroad claims. But prior art wins...

 

[H_K]

Here’s the first detailed view of the Racer that I’ve seen... from a CleanSky event.

Clean Sky VirtualFair

It shows what looks like a SAR configuration, with an internal hoist that swings out. The cabin looks rather small for that mission, more like H135 size. Certainly smaller than H145 or H160. Maybe 6 pax or 4 VIPs?

So perhaps this will be a smaller/lighter helicopter than many were thinking.

 

[VTOLicious]

Here’s the first detailed view of the Racer that I’ve seen... from a CleanSky event.

Clean Sky VirtualFair

It shows what looks like a SAR configuration, with an internal hoist that swings out. The cabin looks rather small for that mission, more like H135 size. Certainly smaller than H145 or H160. Maybe 6 pax or 4 VIPs?

So perhaps this will be a smaller/lighter helicopter than many were thinking.

You are right, the cabin looks rather small... Here is another Airbus slide, hinting EMS/SAR as one of the primary missions.

 

[yasotay]

Here’s the first detailed view of the Racer that I’ve seen... from a CleanSky event.

Clean Sky VirtualFair

It shows what looks like a SAR configuration, with an internal hoist that swings out. The cabin looks rather small for that mission, more like H135 size. Certainly smaller than H145 or H160. Maybe 6 pax or 4 VIPs?

So perhaps this will be a smaller/lighter helicopter than many were thinking.

You are right, the cabin looks rather small... Here is another Airbus slide, hinting EMS/SAR as one of the primary missions.

Perhaps they are going to try a medical rotorcraft first to test the market interest before going to larger aircraft. There is also the chance that the picture was of an earlier configuration that was explored (not wanting to show off certain aspects of the current air vehicle), but not considered for development.
Also thank you H_K for the link to Clean Sky.

 

[TomcatViP]

I think you are looking too much in it. There is no more mystery than an architect building you a 90% scaled house of what was offered to save on material and manpower cost.

There is also the draw on the power available from the twin pusher rotor. Think that torque systems can eat away 10 to 15 % of engine available. Here you have twice the power requested in a cumbersome angled arrangement. Add also the extra drag of the wing sets (penalizing both on downwash, drag as weight induced drag) and you have a tiny platform left to find a function.

 

[H_K]

@TomcatViP I don’t understand what you’re saying, from a physics perspective.

1) Why would this require twice the torque? (Torque is a function of main rotor power, not the # of anti torque devices)
2) Doesn’t a wing also create lift, which more than offsets drag (by definition)?

I see this rather the opposite... this looks like a very aerodynamically efficient arrangement, offering improved lift/drag both at normal cruise speeds and fast cruise speeds that normal helicopters can’t achieve. The only question is the extra installed weight - specifically how much of the performance and efficiency gains are cancelled out by the weight increase.

 

[TomcatViP]

My dear @H_K, lift offset weight. Power, drag.
I would invite you to re-read your high-school point mechanics cursus. Everything is there to grab the concepts more than intuitively.

I would agree however that "twice" sounds erroneous. My intended meaning was more double, two time etc...and was not quantitative.

 

[TomcatViP]

Expect some delays:

Airbus Helicopters is pushing off the first flight of its compound Racer—which stands for rapid and cost-efficient rotorcraft—to 2022. A company spokesman said the delay was the result of “the slowdown of several production lines caused by the pandemic.”

When initially announced in 2017, Airbus said Racer would begin flights in 2020.

Airbus Racer First Flight Pushed to 2022 | AIN

Airbus will begin final assembly of the first Racer compound helicopter in the coming weeks.

www.ainonline.com

 

[H_K]

Airbus Racer slowly starting to take shape:

Fuselage from Romania.
Cockpit section from Germany.
Doors from Austria.

Assembly expected to be complete « mid 2021 » with a first flight by « summer 2022 », roughly 18 months behind schedule.

Capacity stated as « 8 to 11 people », which I believe must include aircrew given the smallish size.

 

[H_K]

Latest update on the Racer here:

Airbus Begins Assembly of Racer Compound Helicopter

Airbus Racer isexpected to demonstrate increased speed and reduced emissions and noise.

www.ainonline.com

​

Interesting tidbits:
- The rotor blades are from the H175
- 6 to 8 seat executive configuration (so I guess 3 rows, 2-2-2 or 3-2-3?)
- 400nm range

All of which hints at a somewhat larger aircraft than what I was expecting (which was more of an H145- or H160-sized cabin).

 

[RavenOne]

It’s taking shape

The Racer programme reaches cruise speed

Assembly of the Racer high-speed demonstrator, an Airbus Helicopter innovation project, has begun following the arrival of its centre fuselage section.

www.airbus.com

 

[TomcatViP]

Notice they didn't even optimize the under floor structure (compare those to the roof mounted structure), probably to help keeping the CG low (those beams looks even massive)...

Refined would wait a little bit longer... (adapted).

 

[H_K]

I also remember reading that Racer needs a taller fuselage profile than normal in order to keep the propellers off the ground and away from the main rotor disc.

As a result there is an incentive to go with a “tall & narrow” fuselage (instead of “short & wide”), with a high underfloor to fit the fuel tanks and landing gear.

 

[VTOLicious]

An article about the joined-wing configuration (Adaption of SAE Technical Paper 2019-01-1884)
https://www.aerodefensetech.com/component/content/article/adt/features/articles/37105

 

[flateric]

https://www.compositesworld.com/articles/leveraging-motorsports-composites-for-next-gen-rotorcraft

 

[flateric]

View: https://www.youtube.com/watch?v=q4ApTk5ZDCs

 

[H_K]

Thanks @flateric. The Racer’s sizing is extremely confusing… the video shows a fairly small cabin, about the size of an H145, ie. 3 rows for 8-9 passengers at most. (Airbus have also told reporters that the cabin is H145 sized)

However, the Clean Sky 2 documents claim that Racer will carry 12 passengers, 350nm, at 220kts, and compare Racer to a 5t notional helicopter that sounds a lot like an H155/S-76/AW169! ie. 1 class up from an H145.

https://www.cleansky.eu/sites/default/files/inline-files/TE-FGA-TR_en.pdf

To make things even more confusing, Clean Sky claims that the Racer’s drive system is sized to carry 16 passengers with a fuselage stretch, without any changes to the engines and gearbox! ie. 2 classes up from an H145

Since Racer will be quite heavy at 7-8 tons (per news reports), this is not a small problem to determine which types it will be competing against…

 

[H_K]

Hi-res image of the Racer in EMS configuration.
Source: www.nzz.ch/mobilitaet/luftfahrt/neues-helikopterprojekt-racer-schneller-weiter-leiser-ld.1579050

Latest news articles from Spain confirm seating for 9 pax, contradicting the official Clean Sky documents (which claim 12 pax) and confirming previous news reports that the cabin is "H145 sized". Any details on weight still TBD.

 

[H_K]

Latest assembly progress:

https://twitter.com/x/status/1490620120682713091

 

[VTOLicious]

"...hybrid-electric stop & start system that reduces fuel burn by 15%..."

What's that?

 

[TomcatViP]

One engine is switched off during cruise. A starter generator is used to spool-up the turbine.

 

[VTOLicious]

Sounds like a feature that could be useful for every multi-engine helo.

 

[totoro]

But not many helicopters might afford shutting off one engine, as not many have wings to aid with the lift when cruising at speed.

 

[VTOLicious]

But not many helicopters might afford shutting off one engine, as not many have wings to aid with the lift when cruising at speed.

Even conventional helicopters do have a reduced power demand in cruise flight. Required power is mainly dependent density altitude and on how much payload is carried. Civil rescue operations (small payload / low altitude) might be a viable use case.

 

[H_K]

Shutting down an engine is obviously easier on Racer because the engines are oversized in order to achieve 220+ knot cruise. So flying on one engine at ~180 knots becomes an interesting option.

However I admit I’m skeptical about the claimed benefit (15% lower fuel consumption at 180kts vs. a conventional helicopter cruising at 130-140kts). It’s unclear whether this marketing claim accounts for the Racer solution’s significant weight penalty...

 

[VTOLicious]

Shutting down an engine is obviously easier on Racer because the engines are oversized in order to achieve 220+ knot cruise. So flying on one engine at ~180 knots becomes an interesting option.

However I admit I’m skeptical about the claimed benefit (15% lower fuel consumption at 180kts vs. a conventional helicopter cruising at 130-140kts). It’s unclear whether this marketing claim accounts for the Racer solution’s significant weight penalty...

"This innovative high-speed formula with a hybrid-electric stop & start system that reduces fuel burn by 15% will take flight later this year."

If I understand correctly it is claimed that the hybrid-electric stop & start system reduces fuel burn by 15%. In any case, he does not make a comparison to a conventional helicopter configuration.

 

[yasotay]

The question is - is that 15% saving total, or for the start and stop procedure?

I suspect their intent is overall, but since there is vagueness, I would not put it past the business development team to use words that allows the reader to develop a misreading of what was said.

 

[H_K]

The question is - is that 15% saving total, or for the start and stop procedure?

For the cruise phase. Sadly the numbers don’t tie for the overall savings… clear as mud:

Airbus infographic:
“-15% fuel consumed per NM at 180kts compared with a helicopter at 130kts”


Tomasz Krysinski, head of R&D:
“At 190 knots we can stop one turbine and fly on only one turbine. It’s much more energy efficient to use one turbine at full power than two turbines at half power. At 190 knots, Racer uses 30% less fuel than a normal helicopter at 130 knots.”
https://www.secretprojects.co.uk/th...ky2-lifercraft-demonstrator.28737/post-415466


Official evaluation report:
“The fuel burn and CO2 metric (kg/pax/km) was seen to increase only by 2.3% to 17.3% over all calculated missions. The overall fuel burn and CO2 increase is easily explained by the higher weight and speed of the new vehicle versus the conventional helicopter.

None of the missions simulated include cruise flight in “eco mode”. This feature has been specifically designed to achieve the ambitious targets in reducing CO2 emissions.

The “eco mode” consists of shutting off one engine during cruise. In that phase of flight, it is more fuel-efficient to use one engine at high power than two engines at medium power. The fuel saving is estimated a 15 percent for a given mission. In just 10 seconds, using a specially-designed electric motor, the idling engine can rapidly and automatically be restored to full power for acceleration, landing or emergencies.

This would deliver on average about a -15% of CO2 on any mission for the cruise phase, bringing the results of the currently simulated missions back down to an overall CO2 reduction instead of a CO2 increase.

This is again mainly due to the improved performance of the new generation engines selected to power the RACER, with a 10% better fuel efficiency and a 25% better power density than the previous generation engines.”

https://clean-aviation.eu/sites/default/files/2021-09/TE-FGA-TR_en.pdf

 

[TomcatViP]

As a summary:
The specificities of the airframe make it necessary to have a twin engines setup when there isn't much use of them during the cruise portion of the flight.
Efficiency would dictate otherwise.

 

[H_K]

@TomcatViP No. Two engines is pretty much standard for all helicopters in order to ensure sufficient OEI performance. Nothing new there. The engines are oversized to fly at 220kts instead of 130-140kts - again quite normal and no different from other fast helicopters. To go fast you need more power.

The efficiency question only comes into play if you don’t need to fly fast for all missions, or if you want to burn less per NM than a conventional helicopter. This scenario doesn’t exist for the US fast rotorcraft which are designed for military use, but it’s an interesting challenge to solve for civilian use.

So the design goal is to be able to cruise at different speeds (220kts and 180kts)… which is good for overall flexibility and is more efficient than a design optimized only for max speed.

 

[TomcatViP]

I can understand the architecture of your argumentation but 15% less consumption at cruise on one engine means that roughly max power available is 2*1/0.85 cruise requirements (2.3).
If we look at the curve below we can see that a rotarywings aircraft can go as fast as the powertrain needed for stationary flight allows them to go.
Moreover, cruise speed is generally defined for a turbine powered aircraft as a high fraction of the maximum speed that the craft can go (I will let the why of that for a further discussion).
Here, the large excess of available power simply illustrates, either that no better engine was available in that power band (doubtful), either that the slow speed regime need much more power than the high speed regime can make of it.
This is not what efficiency dictates...

 

[H_K]

Moreover, cruise speed is generally defined for a turbine powered aircraft as a high fraction of the maximum speed that the craft can go

Normal cruise will be 220kts.
Economy cruise will be 180kts.

Normal cruise is the primary mode and will be at a high % of available 2-engine power. Economy cruise is an option that no other fast rotorcraft currently has and that will enable the Racer to be cost competitive with a slow conventional helicopter (which no other fast rotorcraft is).

I’m not sure what the problem is?

P.S. The curve you posted isn’t relevant because blade stall is not a factor in fast rotorcraft (almost by definition).

 

[TomcatViP]

Thanks for the details.

Blades stall however is common to all rotorcraft. The effects are just tamed and happen later on the faster ones*.
The curve is typically representative of all rotorcraft.

*do not pay too much attention to the speed range.