After being prompted by a story about a Grumman Tiger flying on the East Coast and flying through a down draft most likely caused by a mountain wave or micro burst, I thought I would tell a brief story about encountering a California downdraft.
We were on our way back from the LA basin. The WX was scuzzy Â… rain, clouds, and some wind with improving conditions as we flew northwest toward our destination, Monterey (MRY).
We departed Ontario (ONT) IFR and flew toward the Coast south of the mountains that ring the LA Basin. We crossed the mountains near Santa Barbara and proceeded up the valley to near Paso Robles. We were cleared to Pebble Beach (PEBBS intersection) Â… at the time I was pleased because we could load PEBBS into the 430 and take a direct course.
There are some mountains that line the coast from Morro Bay up to the Monterey/Carmel area. They rang in height but generally are from 4,000 to 5,000 MSL. We were at 8,000. The wind at our altitude was from the west at about 35 to 40 knots. I was somewhat concerned that we could experience some turbulence, which my bride absolutely hates, on the lea side of the mountains, but I thought we should be high enough that turbulence should not be a problem We were “on top” with clouds below that did not look unusual.
Our route of flight was taking us over the coastal mountain range. We were not experiencing any turbulence. The autopilot was behaving itself Â… holding altitude and flying the heading bug. As I monitored the flight I began to feel and sense some changes in the attitude of the plane coupled with a drop in IAS. I checked the engine gauges Â… everything was normal. Despite the fact that we were in the clear, I checked to make sure we hadn't picked up any ice Â… none. We continued to lose airspeed as the autopilot maintained altitude. I disengaged the autopilot and found the controls normal in every respect. I continued to trade airspeed to maintain altitude just as the autopilot had been doing. Our airspeed dropped from 145 KIAS to about 100 KIAS and we were holding 8,000. I checked position and reasoned that it was a mountain downdraft Â… even at 8,000 Â…. but the ride was surprisingly smooth. I had re-engaged the autopilot and continued course as we were almost on the Western side of the mountain range.
In about 2 to 3 minutes the situation began to change. Now the airspeed was increasing. In short order, we were near the yellow arc as the autopilot was “descending” to maintain altitude. I reduced power to keep the airspeed from climbing further. About 20NM from PEBBS we were cleared to 6,000. We still had a few more hills to cross and I descended slowly to 6,000 and onto MRY without incident.
When we stepped out of the plane we were both surprised to feel just how much surface wind there was. The only time we felt much turbulence was on short final. Other than that we had a smooth ride. If I hadn't said anything to my bride, she might not have known there was an issue at all. Don't let the smooth and roomy ride fool you Â… we can still be had. Pay attention the warnings signs can be subtle. Keep the shiny side up and as AVWEB has a penchant for saying: "You all be careful out there!"