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Search: Posts Made By: riff_raff
Showing results 1 to 35 of 601
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Forum: Rotorheads
23rd Feb 2020, 20:35
Replies: 61
Views: 22,655
Posted By riff_raff

dangermouse - Your comment regarding the...

dangermouse -

Your comment regarding the number of motors and reliability/failure rates is correct. Below is a typical fault tree for an electro-mechanical flight control actuation system. The...
Forum: Rotorheads
22nd Sep 2019, 03:36
Replies: 444
Views: 155,182
Posted By riff_raff

Haven't seen the actual RFI document yet....

Haven't seen the actual RFI document yet. Responses to some sections are due Nov. 22 and responses to other sections are due Jan. 1. Be interesting to see if they get any proposals for innovative...
Forum: Military Aviation
29th Aug 2018, 04:11
Replies: 44
Views: 11,827
Posted By riff_raff

Remember how the US liberal media mocked Admiral...

Remember how the US liberal media mocked Admiral Stockdale when he ran as VP in the '92 election? James Stockdale's military record was one of the most impressive in US history, yet he was not...
Forum: Rotorheads
27th Jul 2018, 02:15
Replies: 16
Views: 4,669
Posted By riff_raff

Just a way for Aston-Martin to get lots of media...

Just a way for Aston-Martin to get lots of media exposure without spending much money.

On the other hand, think about other recent ventures into the aircraft sector by auto OEMs that involved...
Forum: Rotorheads
9th Jul 2018, 03:43
Replies: 1,949
Views: 1,584,686
Posted By riff_raff

I have some experience with epicyclic gear drive...

I have some experience with epicyclic gear drive design. And when I looked at a cross section drawing of this gearbox, one thing that seemed questionable to me was the rim section thickness of the...
Forum: Rotorheads
7th Jun 2018, 05:16
Replies: 216
Views: 98,280
Posted By riff_raff

Hearing the claims about "redundancy" made in the...

Hearing the claims about "redundancy" made in the video reminds me of the classic line from Princess Bride, “You keep using that word, I do not think it means what you think it means.”

Redundancy...
Forum: Tech Log
13th Jan 2018, 07:33
Replies: 46
Views: 15,563
Posted By riff_raff

There are two types of AC power generators....

There are two types of AC power generators. Variable frequency and constant frequency. Constant frequency generators (or IDG's) use a variable speed transmission to maintain a constant speed at the...
Forum: Military Aviation
7th Jan 2018, 07:27
Replies: 2
Views: 2,491
Posted By riff_raff

A few years back i was at a MLB playoff game at...

A few years back i was at a MLB playoff game at Angel Stadium. Just prior to the game a C-17 performed a low altitude flyover at very low speed with flaps extended and engines roaring. The noise was...
Forum: Engineers & Technicians
28th Dec 2017, 03:12
Replies: 15
Views: 5,186
Posted By riff_raff

Even for use on a race car, you should perform...

Even for use on a race car, you should perform NDI and dimensional checks to make sure the fastener is in good condition. Unfortunately, this might cost almost as much as a new similar fastener from...
Forum: Engineers & Technicians
24th Dec 2017, 02:52
Replies: 15
Views: 5,186
Posted By riff_raff

As noted by others, the part no. prefix used by...

As noted by others, the part no. prefix used by Boeing for their standard bolts is BACB.

The OP did not mention the specific application he "was trying to use the bolts for". But normally it would...
Forum: Military Aviation
20th Dec 2017, 02:01
Replies: 37
Views: 16,985
Posted By riff_raff

I believe the USN just released their final RFP...

I believe the USN just released their final RFP for the MQ-25 back in October. Since they built a flight demonstrator before the RFP was released, Boeing must think they have a good chance to prevail...
Forum: Tech Log
14th Dec 2017, 05:05
Replies: 39
Views: 18,320
Posted By riff_raff

Didn't you mean density rather than weight?...

Didn't you mean density rather than weight? Actually DU is about 68% denser than lead.
Forum: Tech Log
12th Dec 2017, 03:47
Replies: 39
Views: 18,320
Posted By riff_raff

I believe the use of DU was discontinued for new...

I believe the use of DU was discontinued for new commercial aircraft designs by Boeing back in the 1980's. Tungsten works just as well. But probably costs more.
Forum: Tech Log
12th Dec 2017, 03:33
Replies: 80
Views: 24,269
Posted By riff_raff

Excellent point. Most of these "flying taxi"...

Excellent point. Most of these "flying taxi" projects I've seen don't seem to appreciate the reality of how difficult it will be getting their vehicle design certified for passenger service in most...
Forum: Rotorheads
11th Nov 2017, 00:20
Replies: 212
Views: 116,803
Posted By riff_raff

AnFI, Sorry for the tardy response. ...

AnFI,

Sorry for the tardy response.

The answer to your first question is that for single path flight critical systems/components, an example of the FAA threshold for catastrophic failure...
Forum: Rotorheads
8th Nov 2017, 06:24
Replies: 212
Views: 116,803
Posted By riff_raff

Unfortunately, the type of testing you describe...

Unfortunately, the type of testing you describe would not likely be helpful. What most people, including many engineers, don't understand is the fundamental purpose for conducting tests. In the...
Forum: Military Aviation
4th Nov 2017, 05:22
Replies: 60
Views: 19,106
Posted By riff_raff

I remember the world record Thrust SSC run in the...

I remember the world record Thrust SSC run in the Nevada desert a few years back. The biggest issue I thought they faced was the shock wave traveling aft between the vehicle and the ground. Turned...
Forum: Rotorheads
2nd Nov 2017, 00:50
Replies: 26
Views: 5,989
Posted By riff_raff

FB- That's a great point about twins being...

FB-

That's a great point about twins being gearbox torque limited under most operating conditions (AEO). While engine performance will typically be adversely affected by lower pressure and/or...
Forum: Rotorheads
29th Oct 2017, 04:47
Replies: 212
Views: 116,803
Posted By riff_raff

AnFI, I did not read that the planet gear...

AnFI,

I did not read that the planet gear spherical roller bearings from the two suppliers actually had different "conformal curvatures" (or osculation ratios). What I recall was that they had...
Forum: Rotorheads
25th Oct 2017, 07:22
Replies: 212
Views: 116,803
Posted By riff_raff

gasax, Your concern about AH not yet having...

gasax,

Your concern about AH not yet having established the root cause of this problem is valid. Unfortunately, it can be extremely difficult or even impossible to diagnose such problems with 100%...
Forum: Engineers & Technicians
8th Oct 2017, 04:01
Replies: 20
Views: 5,979
Posted By riff_raff

I have spent over 25 years as a mechanical...

I have spent over 25 years as a mechanical systems design engineer working on military and commercial aircraft programs, and both manned and unmanned space vehicle projects. I've heard dozens of...
Forum: Rotorheads
8th Oct 2017, 01:23
Replies: 129
Views: 101,553
Posted By riff_raff

Good point about the AW609. Looking at the...

Good point about the AW609. Looking at the picture below shows that area of the AW609 to be fairly well protected from impacts with the nacelle tilted vertical.
...
Forum: Rotorheads
5th Oct 2017, 23:40
Replies: 129
Views: 101,553
Posted By riff_raff

"The exposed hardware when the nacelle is in VTOL...

"The exposed hardware when the nacelle is in VTOL mode looks vulnerable to bird strike..."

Interesting how that area was blurred-out of the photo and video provided in the article linked by...
Forum: Tech Log
21st Sep 2017, 01:52
Replies: 9
Views: 3,475
Posted By riff_raff

Some commercial jets have an EE bay just below...

Some commercial jets have an EE bay just below the forward galley. I recall that the 737 NG models have a drip tray located at the top of each avionics rack to collect spilled liquids that seep past...
Forum: Military Aviation
15th Sep 2017, 04:35
Replies: 23
Views: 7,267
Posted By riff_raff

That Desktop Metal machine is limited to a part...

That Desktop Metal machine is limited to a part size of around 13". And if the finished part requires close tolerance interfaces, it will probably need to be finish machined using conventional CNC...
Forum: Military Aviation
13th Sep 2017, 02:30
Replies: 23
Views: 7,267
Posted By riff_raff

It took SpaceX almost 6 years (2002 to 2008) to...

It took SpaceX almost 6 years (2002 to 2008) to achieve the first successful launch of their Falcon rocket. The company model DARPA should be trying to emulate is North American Aviation during the...
Forum: Military Aviation
11th Sep 2017, 03:13
Replies: 23
Views: 7,267
Posted By riff_raff

This idea sounds wonderful on a Powerpoint...

This idea sounds wonderful on a Powerpoint presentation. But I can't see how it would be possible to quickly achieve a production rate of 500 units/month "on-demand". The proposal to produce the...
Forum: Rotorheads
9th Sep 2017, 03:10
Replies: 216
Views: 98,280
Posted By riff_raff

That's funny. Except it should be "the dreaded 36...

That's funny. Except it should be "the dreaded 36 motor approach".

Unfortunately, there are quite a few practical issues with this concept that they do not seem to have fully resolved yet.
...
Forum: Tech Log
3rd Sep 2017, 07:24
Replies: 118
Views: 27,669
Posted By riff_raff

Actually, the brakes only stop the wheels/tires....

Actually, the brakes only stop the wheels/tires. It's the tire contacts with the runway surface that stops the aircraft. You can estimate the amount of heat energy that would need to be rejected by...
Forum: Rotorheads
3rd Sep 2017, 06:41
Replies: 129
Views: 101,553
Posted By riff_raff

Pretty sure they provided adequate clearance...

Pretty sure they provided adequate clearance between the rotor tip sweep and MLG sponson surface under all anticipated operating load/deflection conditions.
Forum: Rotorheads
1st Sep 2017, 06:08
Replies: 129
Views: 101,553
Posted By riff_raff

Good work by Bell. The effort involved just to...

Good work by Bell. The effort involved just to construct that test stand was more than people realize. Hope the inlet airflow to those T64 engines is OK.
Forum: Military Aviation
26th Aug 2017, 07:53
Replies: 7,470
Views: 2,406,029
Posted By riff_raff

Can you tell me what contribution American...

Can you tell me what contribution American engineer Paul Bevilaqua made to the F-35B design? Never heard of the guy, right?

https://youtu.be/w_Iw3Z6Dh8g
Forum: Rotorheads
22nd Aug 2017, 05:06
Replies: 488
Views: 209,140
Posted By riff_raff

Sans- In this video of a tie-down run of...

Sans-

In this video of a tie-down run of the S-97 you can see how the pusher prop drive is de-clutched as the main rotors come up to speed. If my understanding is correct, doesn't the S-97...
Forum: Engineers & Technicians
14th Aug 2017, 04:40
Replies: 11
Views: 2,676
Posted By riff_raff

In the US, OSHA regulations cover work...

In the US, OSHA regulations cover work conditions.

https://www.osha.gov/SLTC/heatstress/
Forum: Rotorheads
14th Aug 2017, 02:51
Replies: 43
Views: 15,397
Posted By riff_raff

Concentric, it says "an overall transmission...

Concentric, it says "an overall transmission efficiency up to 96.5% at min cruise power (LoL test condition)".

A couple things to consider with this claim. What losses are included in that...
Showing results 1 to 35 of 601
 
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