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Search: Posts Made By: HissingSyd
Showing results 1 to 35 of 45
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Forum: Rotorheads
10th Sep 2022, 21:57
Replies: 79
Views: 13,161
Posted By HissingSyd

That was me a month ago, on being pointed to the...

That was me a month ago, on being pointed to the AP3456 online and discovering its use of my own class notes from 1977. This stimulated me into doing something that has been in the back of my mind...
Forum: Rotorheads
16th Aug 2022, 16:12
Replies: 79
Views: 13,161
Posted By HissingSyd

The effect of which I speak is quite subtle....

The effect of which I speak is quite subtle. Seeing the instruments was not a problem.

I suspect that your vibration is likely to be caused by interaction with complex vortices, as is the...
Forum: Rotorheads
16th Aug 2022, 13:29
Replies: 79
Views: 13,161
Posted By HissingSyd

It is also accompanied by vibration, because the...

It is also accompanied by vibration, because the inflow angle only changes at the front of the rotor disc and the effect is assymetric until the airflow regime for forward flight is established. In a...
Forum: Rotorheads
14th Aug 2022, 18:29
Replies: 79
Views: 13,161
Posted By HissingSyd

It might be worth emphasising that all the forces...

It might be worth emphasising that all the forces that the rotor exerts on the helicopter are transferred through those hinges/supports. For a fully-articulated rotor head that force is just the...
Forum: Rotorheads
14th Aug 2022, 14:46
Replies: 79
Views: 13,161
Posted By HissingSyd

I agree. Many of the diagrams in my class notes,...

I agree. Many of the diagrams in my class notes, that then found their way into AP3456, had their inspiration there.



You can look at a copy at...
Forum: Rotorheads
11th Aug 2022, 18:09
Replies: 79
Views: 13,161
Posted By HissingSyd

Well, not a nghtmare, but a huge flashback! ...

Well, not a nghtmare, but a huge flashback!

When I took over as CGI at Culdose in 1976, the available PoF teaching materials were "somewhat lacking in rigour" and I determined to to improve them....
Forum: Rotorheads
10th Apr 2022, 18:43
Replies: 196
Views: 19,352
Posted By HissingSyd

Here is a suggestion. It is not only the tip...

Here is a suggestion.

It is not only the tip vortices, but also the root stall that allows the vortex ring state.

The steady increase in DA would have increased the stalled area, perhaps to a...
Forum: Rotorheads
6th Apr 2022, 13:08
Replies: 57
Views: 16,552
Posted By HissingSyd

I was too succinct. You got it, but the following...

I was too succinct. You got it, but the following posts suggest I was misunderstood.

The ROC, or vertical speed, indicator only shows +-2000 fpm. In an auto in a Wasp you had no idea how fast you...
Forum: Rotorheads
5th Apr 2022, 13:06
Replies: 57
Views: 16,552
Posted By HissingSyd

Didn't the ROC max out at 2000 fpm?

Didn't the ROC max out at 2000 fpm?
Forum: Rotorheads
14th Jan 2022, 17:30
Replies: 119
Views: 18,483
Posted By HissingSyd

"There I was" - I had a bird strike during a...

"There I was" - I had a bird strike during a ground run. When we picked up the pieces we found the pigeon's name and address printed under its wing. ;-)
Forum: Rotorheads
10th Nov 2021, 14:10
Replies: 2,047
Views: 1,306,476
Posted By HissingSyd

Thanks for pointing me to that. It does strike a...

Thanks for pointing me to that. It does strike a memory of loosing a light when getting close inshore. However, I also remember how much the loom could be seen in poor visibility and for much longer...
Forum: Rotorheads
10th Nov 2021, 12:20
Replies: 2,047
Views: 1,306,476
Posted By HissingSyd

This is something that has bugged me from the...

This is something that has bugged me from the very beginning and rather pushes the question of NVG to one side.

They were flying straight towards a lighthouse flashing every 12 sec - an intense...
Forum: Rotorheads
14th May 2021, 15:37
Replies: 134
Views: 15,619
Posted By HissingSyd

My first EOLs were in the Whirlwind 7 in 1971, to...

My first EOLs were in the Whirlwind 7 in 1971, to grass, and were so gentle that you did not expect a run-on. It was said that if you missed the spot you could take off and air taxi to the correct...
Forum: Rotorheads
24th Dec 2020, 09:51
Replies: 146
Views: 24,592
Posted By HissingSyd

It is midnight, mid-winter in the North Atlantic...

It is midnight, mid-winter in the North Atlantic in a Force 10 storm. I am sitting in my Wasp perched atop the hangar/flight deck of HMS Tartar. I am lashed to the deck and the swivel link is on, but...
Forum: Rotorheads
20th Dec 2020, 10:54
Replies: 146
Views: 24,592
Posted By HissingSyd

I think a lot of the discord here comes from...

I think a lot of the discord here comes from different understandings of 'gyroscope'.

To me a gyroscope is a symmetrical solid object rotating fast enough to exhibit rigidity in space.

The...
Forum: Rotorheads
20th Dec 2020, 10:29
Replies: 146
Views: 24,592
Posted By HissingSyd

That paragraph you quote looks very similar to a...

That paragraph you quote looks very similar to a note I wrote for the local beefers in1977 to try to persude them to stop calling phase lag 'gyroscopic precession'.

My teaching materials did/do...
Forum: Rotorheads
17th Dec 2020, 10:52
Replies: 146
Views: 24,592
Posted By HissingSyd

Indeed it is. Phase lag has almost nothing to do...

Indeed it is. Phase lag has almost nothing to do with gyroscopic effects nor with forces and their delayed effects. It is almost entirely an aerodynamic effect - a result of flapping to equality of...
Forum: Rotorheads
17th Dec 2020, 10:31
Replies: 146
Views: 24,592
Posted By HissingSyd

+1 It is about frames of reference. Choose...

+1

It is about frames of reference. Choose inertial or choose rotating, but not both at the same time.

For me the inertial frame and conservation of angular momentum is simplest in giving an...
Forum: Rotorheads
1st Oct 2020, 21:57
Replies: 45
Views: 11,274
Posted By HissingSyd

Not all of them. ;-)

Not all of them. ;-)
Forum: Rotorheads
1st Oct 2020, 18:41
Replies: 45
Views: 11,274
Posted By HissingSyd

Excellent use of physics there.:ok: Tilting...

Excellent use of physics there.:ok:

Tilting the the rotor happens, but didn't we establish in the earlier thread that there is also a main rotor head roll couple owing to offset blade hinges and...
Forum: Rotorheads
4th Jul 2020, 18:27
Replies: 111
Views: 15,722
Posted By HissingSyd

That is where I got the picture above from. At...

That is where I got the picture above from. At least as interesting is this:

The flow around a helicopter is very complex; it becomes much more complex when it comes close to the ground. The...
Forum: Rotorheads
4th Jul 2020, 14:07
Replies: 111
Views: 15,722
Posted By HissingSyd

https://cimg7.ibsrv.net/gimg/pprune.org-vbulletin/...

https://cimg7.ibsrv.net/gimg/pprune.org-vbulletin/837x604/groundvortex_88c9ad7831020677dcdc567ec8e46829e3ee9ae1.jpg
Here's an interesting picture from a paper on Ground Vortex. ;-)
Forum: Rotorheads
3rd Jul 2020, 12:29
Replies: 156
Views: 42,949
Posted By HissingSyd

Of course. Exactly as you describe. Nevertheless,...

Of course. Exactly as you describe. Nevertheless, pretty useful as a student. ;-)
Forum: Rotorheads
3rd Jul 2020, 09:56
Replies: 156
Views: 42,949
Posted By HissingSyd

I came to that conclusion from my personal...

I came to that conclusion from my personal experience early in the previous topic.



It is impossible to describe the sensation or to train for it, but good, current IF experience must help, and...
Forum: Rotorheads
18th Jun 2020, 18:17
Replies: 156
Views: 42,949
Posted By HissingSyd

Oh yes they do. But as you observe, the visual...

Oh yes they do. But as you observe, the visual system usually makes it natural to ignore the phenomenon. When visual clues are reduced, say in hazy weather or at night, it becomes more obvious.
...
Forum: Rotorheads
25th Mar 2020, 10:31
Replies: 115
Views: 26,727
Posted By HissingSyd

I wondered whether to mention dynamic rollover....

I wondered whether to mention dynamic rollover. In this case there is a pivot and it is critical to what happens. Is this thread-drift too far now?
Forum: Rotorheads
24th Mar 2020, 16:54
Replies: 115
Views: 26,727
Posted By HissingSyd

Don't forget I am also ex-RN. Are you posing a...

Don't forget I am also ex-RN. Are you posing a problem of ship stability with CG and Centre of Flotation? ;-)
Forum: Rotorheads
24th Mar 2020, 15:24
Replies: 115
Views: 26,727
Posted By HissingSyd

When the aircraft is moving all bets are off as...

When the aircraft is moving all bets are off as far as I am concerned. What happens does depend on the position of the CG but also in the Centre of Inertia, which is probably as far as this forum...
Forum: Rotorheads
24th Mar 2020, 14:02
Replies: 115
Views: 26,727
Posted By HissingSyd

Here is a secret. Physicists prefer to deal with...

Here is a secret. Physicists prefer to deal with steady state conditions because they are relatively easy to analyse. They ignore how the steady steady was arrived at. Sometimes you can fudge the...
Forum: Rotorheads
24th Mar 2020, 10:45
Replies: 115
Views: 26,727
Posted By HissingSyd

All that is familiar, but it is describing the...

All that is familiar, but it is describing the dynamic response and analysing that is way beyond my pay grade.
Forum: Rotorheads
24th Mar 2020, 10:41
Replies: 115
Views: 26,727
Posted By HissingSyd

The essence of a helicopter in the hover is that...

The essence of a helicopter in the hover is that it does not move or rotate - it is in static equilibrium - and there is no axis of rotation. It means that the sum of linear forces is zero and the...
Forum: Rotorheads
23rd Mar 2020, 10:24
Replies: 115
Views: 26,727
Posted By HissingSyd

I do not know how long ago that was, but when I...

I do not know how long ago that was, but when I started teaching PoF in the 70s they were still quite widespread. Even Shawberry was turning out QHIs with traces of them. Their teaching materials...
Forum: Rotorheads
23rd Mar 2020, 09:58
Replies: 115
Views: 26,727
Posted By HissingSyd

I am ok on this one, I hope. A couple is a vector...

I am ok on this one, I hope. A couple is a vector - it has direction and magnitude. The direction for a couple is parallel to the axis of rotation. It does not have a point of application as such. -...
Forum: Rotorheads
23rd Mar 2020, 09:32
Replies: 115
Views: 26,727
Posted By HissingSyd

Good morning everyone. It is only the exceptional...

Good morning everyone. It is only the exceptional circumstances I find myself in that have tempted me out of my shell. I hope I can be forgiven for raising a bit of diverting controversy.

I have...
Forum: Rotorheads
22nd Mar 2020, 16:54
Replies: 115
Views: 26,727
Posted By HissingSyd

Nil, of course, but I did once read a lot of...

Nil, of course, but I did once read a lot of information from Westland, Boscombe Down and what I think is now the US DCIT. I also had some access to the Sikorsky manual mentioned in the parallel...
Showing results 1 to 35 of 45
 
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