I realise I am asking about an old post, but doesn't it have at least 30 rotating dynamic components by way of all those ducted fans? Doesn't seem simple to me. I assume all fans need to be in good working order prior to any proposed flight.

The 8th anniversary of this thread!

​​​​​​Lillium have just announced they will show at European Business Aviation Convention....a full size model and a flight sim!

https://www.facebook.com/share/8rfMX...ibextid=xfxF2i

8 Years! Wow, that must mean this bird has been certified some time ago and is flying by the hundreds between our various metropolises right?

​​​​​​​About the same rate of production as Hill Helicopters....

Lilium letter to shareholders states that it plans full size manned test flight by years end. This looks like it will be manufactured on their new production line.

https://lilium.com/newsroom-detail/l...eholder-letter

Mjb

I guess “plans” is one of those “forward looking statements” that they define further down in the shareholder letter.

“This press release and the shareholder letter referenced herein contain certain forward-looking statements within the meaning of the U.S. federal securities laws.

These forward-looking statements generally are identified by the words “anticipate,” “believe,” “could,” “expect,” “estimate,” “future,” “intend,” “may,” “on track,” “plan,” “project,” “should,” “strategy,” “target,” “will,” “would” and similar expressions. Forward-looking statements are predictions, projections, and other statements about future events that are based on management’s current expectations with respect to future events and are based on assumptions and are subject to risk and uncertainties that are subject to change at any time.

Actual events or results may differ materially from those contained in the forward-looking statements.”

They seem to be flying since some time. Why don't they just show a vehicle flight demo, manned or not, say at Farnborough?

Lots of info in this discussion about business models, production and flight testing.
Well worth watching, how to certify a new airframe 101.

Manned flight by year end.
Initially serving Regional shuttle transport, 6 seater, 200kms
Low running costs low maintenance "almost nothing to maintain" so very high use.

Globally 40,000 evtol shuttle aircraft by 2035
Lillium has 1050 employees to begin the production phase.

Building 3 fullsize flyable aircraft this year plus 3 other aircraft to assist certification.
Certification of production aircraft following 18 months flight testing, so two years until paying passengers.
Light at the end of the tunnel...
$1.5Billion from China, other funds but more funds needed.
Order book of 700 aircraft, 70 are confirmed.
In terms of safety, certify 10 power 9, aircraft is "as safe as an Airbus A350"

Really? So also fully de-iced and IFR capable? Or only that safe in Dubai where the suns shines all year round and the temps stay above 25?
Oh, wait… are those batteries ok with 50 degrees OAT?

Unpacking this sales pitch to ignorant investors;

Lillium aircraft have near zero parts that fatigue, require periodic lubrication, wear out, or suffer component failures. The physics law of entropy has been repealed.

Assuming an optimist certification in 2026, production will average 40,000 / 9 = 4,444 aircraft per year, or approximately 90 units per week. In the history of aircraft manufacturing, has any one aircraft achieved this rate of production?

If the Lillium is as safe as a AB 350, why not just certify to all the existing EASA/FAA Part 25 and 29 regulations?

Maybe recent advancements in auto industry can be applied to aviation, does a giga press have a significant role to play in fuselage manufacturing?

Mjb


​​​​​​

Maybe it would be a good moment for some reality check? Those assumed future production numbers are pure fantasy. Let's see the product flying first and then watch the market response.

For one, none of the powered-lift aircraft are considered transport category so it would have been Part 23 and Part 27. Unfortunately to use those regulatory parts for an eVTOL or AW609 certification would require an excessive amount of exemptions and other work arounds.

The FAA had used the 23/27 route initially but ran into issues so they made a right turn and elected to follow the EASA lead and write a new regulatory Part for powered-lift. However, to keep things moving until a new part can be written, the 609, Joby, Archer, etc aircraft are being certified as a Part 21.17 Special Class aircraft which cherry-picks various individual regulations from various certification Parts.

wrench1,

The AB 350 was certified under Part 25.1309 which requires system safety analysis proving <E-9 probably of catastrophic failure. Part 29.1309 for rotorcraft has similar section to meet the CAT A performance requirement. These section requirements for system safety are not included in 23 and 27.

If Lillium is claiming that they are as safe as an AB 350, (or a 609) they need to show they meet the requirements laid out in 1309 for Probability of catastrophic failure.

Part 23 and 27 address those same requirements under their respective x.1309 sections. However, Part 23 was rewritten about 7 yeats ago and the current 23.1309 was moved to a different standard format.

And they will from what I've seen written in the current and future power-lift certification guidance. That same guidance actually increases the use of failure probability limits across a larger number of certification requirements since the guidance is performance based. So its quite possible once certified the Lillium or other power-lift aircraft will be technically equal to or possibly exceed the AB 350 failure probability requirements.

wrench,

Unless there is an update to the Part 27 FARs I am unaware of, 27.1309 is limited to the following:§ 27.1309 Equipment, systems, and installations.

(a) The equipment, systems, and installations whose functioning is required by this subchapter must be designed and installed to ensure that they perform their intended functions under any foreseeable operating condition.

(b) The equipment, systems, and installations of a multiengine rotorcraft must be designed to prevent hazards to the rotorcraft in the event of a probable malfunction or failure.

(c) The equipment, systems, and installations of single-engine rotorcraft must be designed to minimize hazards to the rotorcraft in the event of a probable malfunction or failure.

(d) In showing compliance with paragraph (a), (b), or (c) of this section, the effects of lightning strikes on the rotorcraft must be considered in accordance with §27.610.
Note the use of the words "in the event of a probable malfunction or failure".

Compare this to Part 29.1309:§ 29.1309 Equipment, systems, and installations.

(a) The equipment, systems, and installations whose functioning is required by this subchapter must be designed and installed to ensure that they perform their intended functions under any foreseeable operating condition.

(b) The rotorcraft systems and associated components, considered separately and in relation to other systems, must be designed so that— (1) For Category B rotorcraft, the equipment, systems, and installations must be designed to prevent hazards to the rotorcraft if they malfunction or fail; or (2) For Category A rotorcraft—

(i) The occurrence of any failure condition which would prevent the continued safe flight and landing of the rotorcraft is extremely improbable; and

(ii) The occurrence of any other failure conditions which would reduce the capability of the rotorcraft or the ability of the crew to cope with adverse operating conditions is improbable.

(c) Warning information must be provided to alert the crew to unsafe system operating conditions and to enable them to take appropriate corrective action. Systems, controls, and associated monitoring and warning means must be designed to minimize crew errors which could create additional hazards.

(d) Compliance with the requirements of paragraph (b)(2) of this section must be shown by analysis and, where necessary, by appropriate ground, flight, or simulator tests. The analysis must consider—

(1) Possible modes of failure, including malfunctions and damage from external sources;

(2) The probability of multiple failures and undetected failures;

(3) The resulting effects on the rotorcraft and occupants, considering the stage of flight and operating conditions; and

(4) The crew warning cues, corrective action required, and the capability of detecting faults.
Note the use of the words in (b) "The occurrence of any failure condition which would prevent the continued safe flight and landing of the rotorcraft is extremely improbable".

Also read the analysis requirements in section(d). Note there are additional sections in 29.1309 following (d), but they do not pertain to this discussion.

So in short, Part 27.1309 requirements for system safety are far less stringent than 29.1309.

Below is a copy/paste straight from the current eCFR Part 27.1309. And below that is a copy/paste of the Part 23.1309 prior to the 2017 rewrite. Both use "extremely improbable" in determining catastrophic failure rates for this section.

But keep in mind, those collective x.1309 sections are merely the catchall for any system or equipment that did not already have its own separate regulatory section failure probability limits. And to add, the regulatory format for the power-lift certification criteria uses a more system specific failure probability requirements than a "catchall" version.

Can't post links at the moment but here is eCFR address:
www.ecfr.gov


§ 27.1309 Equipment, systems, and installations.

The equipment, systems, and installations whose functioning is required by this subchapter must be designed [...]

(b) Each item of equipment, system, and installation must be designed and installed so that:

(1) The occurrence of any catastrophic failure condition is extremely improbable;

>>>>>>
§ 23.1309 Equipment, systems, and installations.

(a) Each item of equipment, each system, and each installation: [...]

[(b)(2)(i)]
(i) The occurrence of any failure condition that would prevent the continued safe flight and landing of the airplane must be extremely improbable;

Historically, how do manufacturers make a case that their aircraft can reach this level of resilience?
X number of flight test hours?
reliance on computer design?
​​​​​​
Lilium is an innovative design, compromised of established technologies, but golly, aviation is renouned for finding the weakest link in a radical new design.
​​​​​

Mjb

The revision to Part 27.1309 appears to be made last year, Amdt. 27-51, 88 FR 8737, Feb. 10, 2023. It will be very interesting to see how the next Part 27 helicopters will meet this requirement. Based on my experience as a DER/EFUM for Part 27 and 29 Flight Control systems, there is currently not a part 27 helicopter in production that can meet this requirement. I am in agreement that 1309 is a catchall for systems not adequately defined in other sections. However, most propulsion and flight control systems in the Lilium are not defined in existing sections.

Due to the Lilium propulsion system configuration, it is more sensitive to vehicle weight than most eVTOLs. At the same time, one of its claimed advantages is a higher cruise speed than other configurations. Historically, part 27 vehicles did not need to meet the birdstrike requirements required under part 29. It will be very interesting to see how Lillium handles the additional vehicle weight required to meet birdstrike requirements. Not only the propulsion systems, but airframe and transparencies.

And that was one of the reasons the feds moved to 21.17 Special Class/new reg part for eVTOLs. This route will handle all requirements to include the propulsion under one roof unless they use or pursue a separate TC'd engine, props, etc.

However, you might be able see how the revised 27 works as the Jaunt Air eVTOL plans to use 27 or 29 to certify its aircraft. Its also the only eVTOL I know of that can autorotate. But it will probably still need a number of 21.17 special conditions docs to complete the process similar to their use for the Bell 525 FBW approval.

Given Lilium is using the EASA SC-VTOL rules, which are performance based like the FAA 21.17 Special Class eVTOL rules, it will depend on how they address bird strikes. They could simply use a non-standard light weight material that satisfies the requirement? Performance based rules allow for alot of out-of-box solutions to meet the goal. But definitely interesting times ahead.