DO-160G Vibration Test for Electric Drives and Gearboxes

[agatefirmament]

Hi all
I'm looking for some advice on the applicability of DO-160G vibration testing to Electric drive and Gearboxes. Electric drive system on EVTOLs and electric aircrafts usually consist of 3 parts, a controller unit, a motor, and a gear box. My question is mostly in two areas:
1. If the entire drive system (CU, Motor and GB) are tested together on the dyno, or a test stand (in which case could include actual the rotors) does that effectively replace the need for a separate DO-160 Vibe test?
2. If we put the drive system on the shaker table, per DO-160 procedures, it requires the LRU to be operating. To effectively test the drive system, you will need a load, which means some sort of dyno. Is this necessary? and then the next part is whether this is feasible?

Thanks

 

[SWComposites]

so ... what is driving the requirement for DO-160 testing? IIRC its not an FAA cert requirement.
is there a problem with the DO-160 test? (other than cost).

 

[agatefirmament]

so ... what is driving the requirement for DO-160 testing? IIRC its not an FAA cert requirement.
is there a problem with the DO-160 test? (other than cost).

why do you say DO-160 is not a cert requirement? Don't you need to do Do-160 on your LRUs to get them certified for commercial aircraft use? which then means Do-160 is needed if the aircraft itself is certifiable? Maybe you are talking about the Part 33?
But yeah, what's prompting this are the usual problems like cost and schedule.

 

[IRstuff]

so ... what is driving the requirement for DO-160 testing? IIRC its not an FAA cert requirement.
is there a problem with the DO-160 test? (other than cost).

Nevertheless, passing DO-160 addresses a lot of airworthiness questions, doesn't it?

 

[SWComposites]

Its usually an OEM requirement. Don't recall it being a cert requirement, but maybe it is; its a systems thing not a structures thing. so I'm less familiar with it.

OP - if you are not the OEM then you should ask your customer these questions.

 

[Ng2020]

Do-160 is not a 'requirement' but can be best described as an faa-recognised means of demonstrating the suitability of systems & equipment to function properly (if required) or not create a hazard when subject to the intended operating environment. The requirement driving this is 2x.1309a (or astm equivalent for post amdt 64 part 23), among others.

do-160 is 1 means, a widely recognised means, but not the only means.

 

[WKTaylor]

Hope this make sense...

I am not 'dialed into all the analysis/testing', etc for eVTOL.. but here are a few thots to chew over... especially for human flight... and e-power-train issues... that don't seemed to have any 'honorable mention'...

Every prop, gear box and motor and their use in combination have unique vibration patterns and modes. AND the more of these power-combinations-per Acft, the more-the-crazier entangled-harmonics are.... pure/transient harmonics and perhaps further entangled by air-flow distortion drunkenly mixed-together. NOW, lets mix in an arbitrary blade or shaft or motor failure(s) at any of the thrust locations/clusters around the core vehicle [fuselage, etc]... the more arbitrary these unique vibration patterns, modes and harmonics can be. anyone her ever flowing in a multi-engine aircraft and had out-of-sync engines? The waa-waa-waa-waa-waa-waaa-waaaa-wawawa can be barely noticeable to insanely distracting. However simply loose the tip of a prop blade... or have power surges or onset of seizure... and many aspects of dynamics can gotohell in an instant. Even on the mundane side of all this... small dynamic Issues can play a part in low amplitude high cycle fatigue.

Also, in a composite aircraft without fuel, there is still a creditable threat for fire from the Li Ion batteries.

And composite airframes will require extra attention to attenuate damage caused by weather/lightning/icing and related electrical issues: electrical/electronic bonding, grounding, shielding, static dissipation, EMI, TRES etc even for internal EE-EL wires and components and the propulsor units and all the flight computers especially.

Also, could these vehicles safely operated in a 'standard [HOT/dry] Arizona dusty road' environment.. and NOT clog/damage motor/battery/blades, endure static-electricity/arcing, systems-gloogiong/cooling etc...???

/NOTE/ A while back, I answered a forum call about 'critical issues for hypersonic flight'... especially combat missiles... and mentioned that many aspects of weather don't appear to have ever been addressed, IE: all launches of hypersonic missiles seemed to be in fairly clear [CAVU] weather. Sooo I asked about weather related issues/testing such as... blistering-hot speed of Mach5 @ +/-1000F skin-temp... hypersonic penetration of rain, snow, ice, dust, swirling gusts, dark of night, etc... which all seemed to be extremely sketchy.
/PS/ I indirectly heard [read] later... that similar issues had 'come to the table' in one of the forums and more study was required.

The physics of mother-nature can be cruel.

 

[RoarkS]

None of the profiles in DO-160 are going to be applicable to eVTOL environments.

It's neat when you're in the lab the Turboprop profiles sound like you're in a turboprop. Helicopter profiles sound like helicopters. eVTOL profiles sound like... they don't exist yet.

You could do the random sine profiles till you're blue in the face hoping you'll sweep through a resonance that you are instrumented to capture then investigate... but how do you know if that's even an issue.

Like someone said before it's a means of compliance... but you have to do testing to even figure out what you're going to test so it has meaning. I was in with some training with some Joby guys a few months back asking similar stuff.

They are flying... instrument the vehicle. figure out vibration profiles. Do dumb stuff that knocks kidney stones loose. onset of transitional lift, vortex ring state, wind loads that put rotors into dirty air. Make your own profile and impress the unit members. If you're members get a seat on the committee, then call up your competitors, someone for gods sake buy Lilium, and put your heads together and get it in the next revision.

BTW I'm a helicopter, SEL airplane, and aerospace engineer... I'd really like to fly one of these things.

 

[Sparweb]

Couple of things are going on in this thread:

• EVTOLs are so new, most engineers (including me) aren't intimately familiar with the cert requirements for these.
• What we do know is that most EVTOLs seem to be getting certification through "new" FAR 23 which is a black box compared to "old" FAR 23.
• The new FAR 23 gives latitude to the applicant to define the standard for themselves (YES!) and then pick their preferred means to meet it.
• DO-160 can be a means to meet the standard (as NG2020 correctly said) but now the self-selected standard might not need testing at all.
• The standard self-selected for any "new" FAR 23 type design is proprietary to the designer, not a public document.
• The standard self-selected for any "new" FAR 23 type design does not have to resemble "old" FAR 23 in any way.
• The preferred means to show compliance are likewise proprietary to the designer.
• Alterations to an existing standard for showing compliance for the purpose of a new standard are equally proprietary.

Therefore...
@agatefirmament , you are almost SOL for help on this forum. Your employer may be sticking close to the former FAR 23 or off wildly on their own with whatever Issue paper they can get away with that an overtaxed FAA doesn't have the time or staff to understand.

Nonetheless I might try this:
q1: If you test the whole drivetrain together you get it done in one big test rather than 3 separate test programmes. Great until you have to change one component of the drivetrain, in which case an individual test won't be sufficient, and you'll have to test the whole drivetrain again. There's no right answer for everyone.
q2: Why not test with the propeller in place? If you want to retort "it's obvious why not", I won't disagree with you, but wait... why not write down all the reasons exactly and specifically why the propeller load must be in place, but the propeller can't be used in the test. This exercise will probably illuminate what you actually need to do. Either that, or go search Google for pictures of aircraft engine test stands, and the answer will be staring you in the face.

But all of my suggestions are based on the tried and true. Your EVTOL probably does not need to obey the same rules as previous aircraft. It certainly doesn't have to obey the same economic rules - at least, not until the day it actually goes on sale. Good luck, and keep your resume up to date.