What benefit would a low airspeed system have?

[Shawn Coyle]

What benefits can you think of that might come from having a system that would accurately show airspeed down to 5 knots (direction as well as amount). It would also show sideslip at all speeds...

[SimFlightTest]

Showing sideslip at all speeds would have the benefit of not having to hear some pilots say that "helicopters do not fly with sideslip". That would add 10 years back to my life!

[RVDT]

Like the one on a "Tupperwolf"?

The bit sticking out of the middle of the beanie? OADS.

http://uscgaviationhistory.aoptero.org/images/HH-65%20Thetis.jpg

Another view

http://avstop.com/news_april_2010/mh-65-c-dolphin_helicopter.jpg

Apparently the VIMI?? system in the Tiger uses swashplate displacement/VTG and computes it from that. Only works adequately with a type with low C of G range though.

Then again a pilot with some semblance of situational awareness and experience could probably tell you the same thing from control displacement and close enough to a visual reference and achieve a similar result. As quoted it would be a bit hard in the dark!!

[topendtorque]

Very neat haircut, that one RVDT.

Trying to think Shawn, certainly any system that could be coupled to ROD and to warning of approaching a recirculating situation would be excellent, especially when you cannot see outside; also maybe the night Ag people would have some comments.

[RVDT]

System on the current horse computes TAS from the ADC and COG and GS from the GPS to bring up a wind barb on the EHSI just like you would see on a weather map. The ADC just sticks it in the GPS automatically most still have a manual option if you have the time or inclination.

Plus or minus 5 knots I would say and of course once you slow down it is not so accurate and will drop out below a certain speed but is close enough for government work!

Then again as I was told many moons ago as a sprog if you don't know where the wind is coming from and how hard - all the time - you shouldn't be in the drivers seat. There are a plethora of cues/clues available.

[Harry the Hun]

Apart from better data for weapon computation I can only think of one advantage:
For once we can fly the sometimes funny CAT A procedures, which are based on airspeed and not groundspeed, acurately by the numbers.

Not that it would allways make sense though. An LDP of 25 knots with 30 Kts of wind would still give you a groundspeed of minus 5, what somehow defeats the purpose, but that is a different topic.

[Geoffersincornwall]

..... don't get me going on that one. There are some Flight Test Engineers that need a reality check.

G. :ugh:

[topendtorque]

Then again as I was told many moons ago as a sprog if you don't know where the wind is coming from and how hard - all the time - you shouldn't be in the drivers seat. There are a plethora of cues/clues available.

rvdt. forgot the bit about, - "even when you are sound asleep"

[HeliComparator]

Shawn, if you think about it, lots of helicopter accidents occur at very low airspeed due, for example, to inadvertantly being downwind, getting into vortex ring or just running out of power. Whether you are doing 70, 80 or 90 kts IAS is of no consequence but whether you are doing 10, zero or -10 is much more important. So its a pity that conventional ASI are accurate in the unimportant range, and inaccurate or in fact non-functional in the important range!

This is why the CAA did some research into a low airspeed algorithm based on control positions, accelerations etc being derived from a neural net type programme. I seem to recall that a lack of reliable "learning" data was the stumbling block that stalled the research.

What sort of system were you thinking of, a mechanical vane-type or a synthesised / algorithmic type? If the former, the kit can be more of a hazard than its worth!

[Shawn Coyle]

Thanks to all for the inputs. Hadn't thought of Vortex Ring State avoidance!
Just trying to put together a proposal to modify a system that may be appropriate.

[jimf671]

... Then again as I was told many moons ago as a sprog if you don't know where the wind is coming from and how hard - all the time - you shouldn't be in the drivers seat. There are a plethora of cues/clues available.

'Winchman' by Colin Murray QGM, pbk, page167.

"... Some pilots can read the mountains like a book. They know exactly where the wind is coming from and they are on top of it all the time. I remember on one occasion, Tim Noble, the deputy chief pilot in Stonoway, turned to Captain John Bentley ... and said, 'John, I believe you're in league with the devil.'

What he meant was that John Bentley was really good at reading every puff of wind, the direction and strength, and knew exactly where every demarcation point was going to be. ..."