Best Route - French Valley to Borrego Valley

[eetrojan]

Best Route? - French Valley to Borrego Valley

I’m planning a short little flight soon and am debating the best route.

If you were flying from French Valley (F70) to Borrego Valley (L08), would you go direct over the mountains at 7500 (or perhaps 9500) with fewer outs for a while, or would you go a little bit to the south, or perhaps to the north, to fly over lower terrain and give yourself a shallower descent into L08?

Here’s a SkyVector sectional: http://goo.gl/zAaUTc
Same route on the SD TAC: http://goo.gl/l4lXTa

If you're a Google Earth user, here's a KML file you can save and then open locally to show the direct route in Google Earth: http://goo.gl/NM9Yza

I’m thinking direct since planes are good at flying straight lines, but welcome contrary advice.

Thanks!

 

[Pilawt]

I'd probably bend the route a little to the north toward Anza, and follow the wash down toward Borrego, so your descent can be more gradual. Adds maybe two or three miles to your straight-line route.

 

[Jeff Oslick]

I've flown this a few times, and I bend the route south a bit towards the Warner Springs gliderport. Be aware that the turbulence warning on the chart is there for a reason.

 

[eetrojan]

Thanks guys.

I didn't see the turbulence warning until you pointed it out, so good to think about. Thanks.

What is the geographic scope of that warning? If I bent the route to the north and followed the wash into Borrego Valley, as suggested by Pilawt, rather than to the south over the Warner Springs glider port, would that turbulence warning still apply?

 

[chartbundle]

Thanks guys.

I didn't see the turbulence warning until you pointed it out, so good to think about. Thanks.

What is the geographic scope of that warning? If I bent the route to the north and followed the wash into Borrego Valley, as suggested by Pilawt, rather than to the south over the Warner Spring glider port, would that turbulence warning still apply?

If winds aloft or at the surface are blowing heavily it pretty much applies over all the terrain in that area. The advantage with going over lower terrain north will be that it will generally be less severe due to the reduced elevation change and you can stay higher to try and stay above it.

 

[Clark1961]

BIG DISCLAIMER: I have never flown in the area.

One of my first thoughts when looking at the sectional was that there would be no place to hide if the wind was blowing from the west. Very easy to get in trouble and not see an obvious way out in that setting.

I flew in a similar setting with 50 Kt winds roughly perpendicular to the axis of the valley. I could not find a smooth ride down low (out of oxygen) but I did manage to stay out of the downdrafts. I ended up on the downwind side of the valley very close to the ground - there should have been lift but it was mostly just turbulent. In this case I might think about going west of the big ridge just to be in rising air with a west wind.

The other thing that caught my eye was the gliderport. Either learn where they operate or give them a very wide berth. The tows and gliders can be just about anywhere. Of course gliders don't fly early unless they are chasing ridge lift.

If a guy tried the high route then they'd end up circling down over their destination. That might not be a bad thing on a high wind day and 9500 would be lowest I'd want to be on a high wind day (50% of the valley to peak elevation change above the highest elevation). For a 45 mile trip it's a lot of time climbing and descending so prolly not worth it.

Definitely a good discussion question.

 

[eetrojan]

Thanks.

I goofed around in Google Earth to create this birds eye view of some possible routes and the terrain. They all assume cruise is at 7500.

The red one is the direct route, 45nm, with a relatively steep descent. I'll have a passenger, so probably best not to do that.

The green one is the "bend north" route, 47nm, that has me arriving via the wash.

The yellow one is the "bend south" route,48nm, that has me me passing near the glider port (yellow star). It doesn't seem to help much with terrain. On the other hand, it has me arriving from the southwest, nicely set up for right traffic on RWY 8 or left traffic on Rwy 26. Both patterns are south of the runway.

The orange one is the "dogleg south" route, 55nm, that has me arriving from the southwest too.

I like the north route best in terms of not increasing the distance much, ground clearance and turbulence avoidance, but the AFD says that there is aerobatic activity to the north side of Borrego Valley airport, from the surface to 5000 feet, so have to think about that a bit.

 

[eetrojan]

*** 9500 would be lowest I'd want to be on a high wind day (50% of the valley to peak elevation change above the highest elevation) ***

Thanks for this. Is this a standard rule of thumb for likely smooth air on a windy day?

 

[Clark1961]

Thanks for this. Is this a standard rule of thumb for likely smooth air on a windy day?

Yup, straight from Imeson's book. Not so much to keep you in smooth air as to keep you out of any downdrafts or rotors that'll drive you into the ground. In practice I just keep climbing on windy days when I have to make the trip and it looks doable other than wind. A key thing on "looks doable" is reading the clouds. If I can see the rotors and work through them or get above them then I'll probably be okay. No rotor clouds and high winds are a little scary...

 

[chartbundle]

I like the north route best in terms of not increasing the distance much, ground clearance and turbulence avoidance, but the AFD says that there is aerobatic activity to the north side of Borrego Valley airport, from the surface to 5000 feet, so have to think about that a bit.

Yes, you definitely want to plan to get south of the field somehow to stay out of that area. The easiest way is probably to transition south while still west of 'town'. Just be cautious if anyone is departing to the west. And realize the aerobatic pilots have a very 'interesting' interpretation of things like pattern altitude and right-of-way if they're out flying.

 

[eetrojan]

Yes, you definitely want to plan to get south of the field somehow to stay out of that area. The easiest way is probably to transition south while still west of 'town'. Just be cautious if anyone is departing to the west. And realize the aerobatic pilots have a very 'interesting' interpretation of things like pattern altitude and right-of-way if they're out flying.

Thanks! That seems simple enough. Sometimes I overthink things.