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Search: Posts Made By: IFMU
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Forum: Rotorheads
24th Jul 2021, 02:42
Replies: 444
Views: 156,048
Posted By IFMU

Think in terms of a fixed wing Cessna with two...

Think in terms of a fixed wing Cessna with two wing fuel tanks. One full, and one empty. You have to put in enough aileron to react the unbalanced fuel load, but the airplane still goes straight....
Forum: Rotorheads
23rd Jul 2021, 09:25
Replies: 444
Views: 156,048
Posted By IFMU

I've got no Sikorsky bosses anymore. I moved to...

I've got no Sikorsky bosses anymore. I moved to another UTC division when they closed Schweizer. I was the responsible engineer for the X2 flight controls though. And yes I've studied physics. ...
Forum: Rotorheads
22nd Jul 2021, 22:41
Replies: 444
Views: 156,048
Posted By IFMU

A conventional helicopter has to react the thrust...

A conventional helicopter has to react the thrust from the tail rotor with lateral cyclic. It's no big deal.

An X2 rotor system would use lateral cyclic, same direction for both rotors, to react...
Forum: Rotorheads
22nd Jul 2021, 22:37
Replies: 444
Views: 156,048
Posted By IFMU

Totally wrong. The coax limitation for yaw is in...

Totally wrong. The coax limitation for yaw is in autorotation. They leave room for differential collective on top of collective.
Forum: Rotorheads
21st Jul 2021, 13:08
Replies: 444
Views: 156,048
Posted By IFMU

Now your rambling is just getting silly. Why...

Now your rambling is just getting silly. Why would you think the prop torque would be a problem? Do you think there is not enough cyclic trim to balance it?
Forum: Rotorheads
15th Oct 2020, 18:03
Replies: 444
Views: 156,048
Posted By IFMU

I agree on all points here.

I agree on all points here.
Forum: Rotorheads
15th Oct 2020, 16:47
Replies: 444
Views: 156,048
Posted By IFMU

So - you are using a linear relationship between...

So - you are using a linear relationship between power and speed? Care to explain?

My quick estimate was by the square root of the increase of power. Also how do you know the weight? Any flight...
Forum: Rotorheads
15th Oct 2020, 14:51
Replies: 444
Views: 156,048
Posted By IFMU

At 2/3 power and 211 kts S&l, I'd project 258 kts...

At 2/3 power and 211 kts S&l, I'd project 258 kts max s&l.
Forum: Rotorheads
15th Oct 2020, 01:46
Replies: 444
Views: 156,048
Posted By IFMU

Defiant at 211 kts s&l, 232 in a descent, 2/3...

Defiant at 211 kts s&l, 232 in a descent, 2/3 prop torque.
https://news.yahoo.com/amphtml/sb-1-defiant-coaxial-demonstrator-131114297.html

https://youtu.be/cNszG1Sefss
Forum: Rotorheads
3rd Sep 2020, 17:32
Replies: 444
Views: 156,048
Posted By IFMU

https://www.verticalmag.com/news/army-pilot-flies-...

https://www.verticalmag.com/news/army-pilot-flies-sikorsky-s97-raider/?utm_source=vertical-daily-news-top-story&utm_campaign=vertical-daily-news&utm_medium=email&utm_term=top-story&utm_content=V1
Forum: Rotorheads
3rd Sep 2020, 02:58
Replies: 444
Views: 156,048
Posted By IFMU

I'd say the rotor is less complicated - it lacks...

I'd say the rotor is less complicated - it lacks a lead/lag hinge. It does have twice as many rotors, if that is what you mean as complicated. And, I'd also give you the fact the upper pushrods go...
Forum: Rotorheads
3rd Sep 2020, 02:55
Replies: 444
Views: 156,048
Posted By IFMU

I used to be a Sikorsky/X2 guy. I'm probably not...

I used to be a Sikorsky/X2 guy. I'm probably not at liberty to say the particulars but I'll say you have your harmonics wrong with respect to what was creating vibes and what wasn't.



I have...
Forum: Rotorheads
26th Jan 2020, 16:48
Replies: 444
Views: 156,048
Posted By IFMU

Because it is in flight test, they will be doing...

Because it is in flight test, they will be doing flights at many different power settings on the rotor, prop, plus horizontal tail position. Each one will give a different attitude for a given...
Forum: Rotorheads
16th Dec 2019, 15:01
Replies: 444
Views: 156,048
Posted By IFMU

The translational airspeed region was not as...

The translational airspeed region was not as challenging as high speed flight in the X2. In fact for most of the lower speed region the X2 vibes could be managed without AVC using only classical...
Forum: Rotorheads
13th Dec 2019, 03:26
Replies: 444
Views: 156,048
Posted By IFMU

We didn't have a clutch on the X2. But you would...

We didn't have a clutch on the X2. But you would clutch up the prop at flat pitch, not MCP. Once it was clutched up you would roll in the prop pitch and start ramping up the power. I am not sure I...
Forum: Rotorheads
12th Dec 2019, 16:57
Replies: 444
Views: 156,048
Posted By IFMU

The X2 vibe levels were not brutal, and in fact...

The X2 vibe levels were not brutal, and in fact were most benign at hover. This is when you would not be spinning the rear gearbox.

Please name one gearbox where the oil is warmed up prior to...
Forum: Rotorheads
16th Nov 2019, 12:40
Replies: 444
Views: 156,048
Posted By IFMU

That's why they don't make decisions based on...

That's why they don't make decisions based on looks! This cracks me up.
Forum: Rotorheads
9th Sep 2019, 20:00
Replies: 444
Views: 156,048
Posted By IFMU

Why would you assume that? They have their own...

Why would you assume that? They have their own radar feed, their own chase aircraft, and for VFR flights are not required to file a flight plan.
Forum: Rotorheads
20th Apr 2019, 20:10
Replies: 444
Views: 156,048
Posted By IFMU

Yep. 252 kts level flight for the X2 and...

Yep. 252 kts level flight for the X2 and something like 262 in a shallow dive.
Forum: Rotorheads
20th Apr 2019, 18:11
Replies: 444
Views: 156,048
Posted By IFMU

Definitely not for the X2. I can't imagine it is...

Definitely not for the X2. I can't imagine it is flight critical for its progeny.
Forum: Rotorheads
19th Apr 2019, 23:08
Replies: 444
Views: 156,048
Posted By IFMU

We did it on the X2. Not just AVC, you need to...

We did it on the X2. Not just AVC, you need to balance too. Most likely the Raider and Defiant guys have gotten further as management during X2 didn't allow as much dedicated vibe work as we would...
Forum: Rotorheads
19th Apr 2019, 22:33
Replies: 444
Views: 156,048
Posted By IFMU

They certainly can, but we were balancing the X2...

They certainly can, but we were balancing the X2 using conventional techniques. Then vibes were cleaned up with AVC. The predominant harmonics are not exactly as you say but not sure if that info...
Forum: Rotorheads
19th Apr 2019, 22:27
Replies: 444
Views: 156,048
Posted By IFMU

If you look at the installed power required for...

If you look at the installed power required for high speed flight, you are more than covered. Also with 8 blades there is enough solidity to absorb the power required for high/hot even without all...
Forum: Rotorheads
19th Apr 2019, 03:26
Replies: 444
Views: 156,048
Posted By IFMU

Jack, When I was recruited to design and build...

Jack,
When I was recruited to design and build the X2 FBW I spent a lot of time studying the ABC and talking to the old timers. Everything you say about the ABC is true. The X2 and its successors...
Forum: Rotorheads
18th Apr 2019, 14:35
Replies: 444
Views: 156,048
Posted By IFMU

Thanks for the link! I hadn't heard they had a...

Thanks for the link! I hadn't heard they had a second flight. Not sure I agree that he was struggling to make the program sound viable, but I don't think he is very knowledgeable about the...
Forum: Rotorheads
28th Mar 2019, 22:40
Replies: 444
Views: 156,048
Posted By IFMU

Here is an X2 story on signed panels. At the end...

Here is an X2 story on signed panels. At the end of the Elmira flight test program at Schweizer, the Florida guys were packing up the aircraft to take it south to do the envelope expansion. The...
Forum: Rotorheads
24th Mar 2019, 14:23
Replies: 444
Views: 156,048
Posted By IFMU

Hey, toothless has a Valor tail to balance out...

Hey, toothless has a Valor tail to balance out the Defiant nose, in case nobody noticed.
Forum: Rotorheads
24th Mar 2019, 14:19
Replies: 444
Views: 156,048
Posted By IFMU

Apparently he is a disgruntled ex-employee of...

Apparently he is a disgruntled ex-employee of Bell. So, he has an axe to grind.
I've never been on facebook but I joined LinkedIn when Sikorsky closed Schweizer and I had to decide where I was...
Forum: Rotorheads
22nd Mar 2019, 21:32
Replies: 444
Views: 156,048
Posted By IFMU

Nice note from Bell Flight congratulating the...

Nice note from Bell Flight congratulating the Defiant team on LinkedIn. Interesting that one of the Bell Flight guys is trashing the Valor and saying Defiant is the way to go. What is up with that?
Forum: Rotorheads
22nd Mar 2019, 10:57
Replies: 444
Views: 156,048
Posted By IFMU

First flight of the X2 was less than 30 minutes. ...

First flight of the X2 was less than 30 minutes. Knowing Sikorsky test they have a build up plan and they will follow it. I don't think Sultana's jibes will change the pace at all. X2 flew 3 or 4...
Forum: Rotorheads
21st Mar 2019, 22:10
Replies: 444
Views: 156,048
Posted By IFMU

Awesome! Looks great! ...

Awesome! Looks great!
https://youtu.be/Sm-N7trI0sw
Showing results 1 to 31 of 31


 
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