Speed record?

On Tuesday, September 20, 2016 at 9:01:26 PM UTC-4, Soartech wrote:
or fantasy of flight?
On page 52 of the September issue of Soaring magazine Jim Payne is listed as having flown an out and return course of 300 km at an average speed of an amazing ground speed of 189.62 MPH ! Can someone please explain how he did this when the Vne of the Arcus M is 174 MPH. It seems to me the only way to do this is to somehow fly (at Vne the entire flight),downwind, on both out and return legs.

A rule of thumb under standard conditions is about 2%/thousand feet increase in True Airspeed. So, if you're indicating 100kts at 10% feet you're actually doing closer to 120kts over the ground in still air.

Now, the problem kicks in with flutter and aeroelasticity, so the VNE (indicated) decreases with altitude in most gliders. I'll leave it at that, since it's been more than 30 years since my last problem set on that topic :-)

P3

Every glider flight manual I studied made it clear that the flight tested limits laid out applied up to 3000 meters ... over that you are relying on a combination of theory, over-design, excessive build over required standards, and it always seemed to me good fortune. I have no idea if such applied to the Arcus M used by Payne.



On Tuesday, September 20, 2016 at 9:01:26 PM UTC-4, Soartech wrote:
or fantasy of flight?
On page 52 of the September issue of Soaring magazine Jim Payne is listed as having flown an out and return course of 300 km at an average speed of an amazing ground speed of 189.62 MPH ! Can someone please explain how he did this when the Vne of the Arcus M is 174 MPH. It seems to me the only way to do this is to somehow fly (at Vne the entire flight),downwind, on both out and return legs.

Jim's a retired USAF test pilot, so I'm sure understands all the intricacies of flying near Vne.

I'm not an aerodynamicist so here's my lay understanding. A glider's Vne is the true airspeed as indicated IAS at typically 3000m. If I recall, my ASH-26E redline was 146 KIAS which worked out to 160-ish TAS. The chart Schleicher provides for Vne above 3000m drops the IAS to keep the TAS at or below 160.

My ASW-27 chart is:
10K 151 knots
16.5K 133 knots
23K 119 knots
etc...

In the '26 I flew a 100 km triangle in wave between 14 and 18K MSL so limited my IAS to a conservative 120 knots, which I maintained nearly the whole time. The achieved speed for the triangle was a bit over 130 knots. So TAS is your friend even below 18K!

If repeating this in the '27 I would again use 120 as a "safe" Vne for below 18K.

5Z

On Wednesday, September 21, 2016 at 6:59:10 PM UTC-7, howard banks wrote:
Every glider flight manual I studied made it clear that the flight tested limits laid out applied up to 3000 meters ... over that you are relying on a combination of theory, over-design, excessive build over required standards, and it always seemed to me good fortune. I have no idea if such applied to the Arcus M used by Payne.