Friday, August 11, 2006

Night Flights, Hearing Voices, & Small Arms Fire

The weather in Northern California the past two weeks has been excellent for flying. Warm, but not too warm. Calm winds and a pressure gradient pattern that has kept the marine layer mostly off the coast. Add to this equation a full moon and you have the perfect setting for a couple of excellent, instructional night flights.

The first was a night flight with an instrument candidate. It was warm and mostly dry with light and variable winds all the way to 6000 feet MSL. With a slight haze, we made our way toward Susin Bay for an LDA practice approach as the sun set over the Pacific. Outbound on the procedure turn was were I caught the first glimpse of the nearly full moon - an unbelievably large Mandarin orange crescent rising from behind the distant Sierra Nevada Mountains. Of course my student couldn't see this, being under what Hamish calls the cone of stupidity. So I did the decent thing and asked my student to look up. He took a few moments to appreciate the sight and, after the requisite oouuhaa, it was back to the salt mines. During the flight, the moon rose higher and higher, bathing the sleeping countryside in a soft, silver light.

The next night involved an hour in the traffic pattern at Oakland so my student pilot could log the necessary night landings. The tower controller was most accommodating, demonstrating light gun signals twice upon request. I usually point out a good landmark like the Hayward Civic Center to help pilots line up on downwind. Last night, the full moon rose from behind the Sunol Ridge and provided the best target imaginable. We did all the landings available on the menu - normal, short field, power off, and the always popular no-flaps landing without cockpit or landing lights.

Yesterday was a flight in the Cirrus to Reno, part of a warm up for the pilot who will be taking a trip over some mountainous terrain. We succeeded in getting the SR22 doors to latch and we were on our way, climbing to 9,500 feet for the trip over the Sierra Nevada. The winds aloft forecast called for 20 knot winds out of the south and as suspected, the ride turned decidedly bumpy as we passed over the Hangtown VOR at Placerville. I find it amusing that the VOR is actually called Hangtown, which was Placerville's infamous moniker during the mid-1800s gold rush, presumably because of the frequent dispensing of hanging as a form of justice.

This was the view as we slipped just northwest of Lake Tahoe.

We climbed to 11,500 feet and things smoothed out a bit, but the winds aloft were higher that what was forecast and pushed our ground speed to just under 200 knots. You can see that pesky ALT2 light is on, indicating it has failed. This has been a recurring problem and the shop just can't seem to get to the bottom of it.

The descent into Reno got bumpy, but close to the surface the winds were calm and the temperature a moderate 30 degrees Celsius. Approach gave us a right base entry to runway 16 left, which gave us time to slow down and descend. On the ground, I made a quick call home. Surprised to learn that I was in Reno, my wife mentioned that she felt lucky and encouraged me to find a slot machine. Alas, I couldn't find a single one-armed bandit in the FBO. So after a short stop for lunch and some very expensive fuel (which reduced the ramp and airport fee), we were on our way back.

With the midday sun shining through clear skies, the climb out of Reno was decidedly more bumpy that when we arrived. During the climb out, following I-80 through the pass, the VSI alternated between 200 feet per minute and 1200 feet per minute - a good indication of the updrafts and downdrafts we were flying through. Now fighting a 28 knot quartering head wind, our ground speed slowed to 145 knots and provided a nice opportunity to discuss strategies for recognizing and avoiding mountain waves as well as other way to maximize passenger comfort. One simple rule is to avoid flights over mountainous terrain when the winds aloft forecast exceed 25 knots. Another guideline is to avoid flying at midday and fly early in the morning or late in the day, when solar heating of the earth's surface is reduced.

We originally planned to cruise back at 10,500, but the ride was so rough we decided to climb to 12,500 for the brief 15 minute ride across the Sierra Nevada. At the pilot's request, we diverted south a bit and descended to get a view of a lake just to the east of Ice House Reservoir. I was surprised to see several aircraft below us appear as targets on the Cirrus' traffic watch. We did a few orbits around the lake, staying above 10,000', as much to avoid the other aircraft as to avoid the turbulence below.

Here's a view of the Sierra Nevada while we were gently banking.

One thing that didn't happen on the entire flight was the annoying terrain warnings I mentioned earlier. Why no "Terrain, pull up!" scoldings? I discovered that a Garmin 396 that was added to this plane as a backup system was actually wired into the audio panel. This fact came to light quite by accident. Seems the other partner in the aircraft was listening to the built-in XM radio on the trip before ours and I immediately heard music when the avionics switch was turned on. I had not realized that the 396 was connected to the audio panel. That's when it occurred to us that the aural terrain warnings must have been coming from the 396. So we turned it off and that simple solution provided a peaceful flight. An interesting lesson on the complicated interactions that are possible when different equipment is connected to the aircraft by different people.

Back at the home base, we were putting the aircraft back in the hangar when I heard what sounded like gunfire. I stuck my head out of the hangar door and saw an airport vehicle involved in bird hazing - trying to scare birds away by shooting firecracker-like ordinance in their direction. I have no idea what sort of equipment is used to do this hazing, but I could see a puff of smoke in the air each time I heard the report from a small explosion. I returned to helping get the plane secured and when I went back out of the hangar, I saw the unintended consequences of the bird hazing. Somehow one of the rounds being shot had sparked a grass fire. Luckily, this airport has fire fighting trucks on the field and the small blaze was quickly extinguished. Bet the birds were scared away, too.


Ron said...

Quite the eventful day! I have not seen the same ALT2 failures when flying Cirruses (Cirri?), however we've had ALT1 and MCU failures. Losing the MCU is particularly nasty from what I've been told.

I imagine it'll get even more interesting once the turbo version is available. More heat in that engine compartment means a harder life for those alternators...

John said...

I hear that the problem with the electrical system's Master Control Unit is oil mist from the engine compartment getting on the circuit board. I even heard that there is a AD or a service bulletin (not sure which) that requires the MCU circuit board to be cleaned and given a new protective coating at every annual inspection.

A complete electrical system failure is sobering and makes the idea of a completely separate attitude indicator (vacuum or alkaline battery driven) look like a pretty good idea. A back-up hand-held GPS and comm radio isn't a bad idea, either.

Tony - Glider CFI said...

Heating of the earths surface really doesnt affect mountain wave. The wave works day and night when the component of wind perpindicular to the drop off is above 20ish knots.

John said...


I agree that mountain wave activity can occur day or night. Solar heating produces an additional set of problems with updrafts and downdrafts that can be uncomfortable and even dangerous to light aircraft. Uneven solar heating is the rule in mountainous terrain where one side of a ridge is exposed to the sun and the other basically shaded. Add a capping layer of stable air on top of the ridge and the result can be a real mix-master below the ridgeline.

To my mind, mountain waves and solar heating are two different mechanisms that can generate strong turbulence.

tony said...

yep thats right john. sorry i thought you were implying that heating enhanced the wave. No doubt that thermals can cause anxiety. Especially out west were 1000 fpm thermals are not uncommon. Many glider pilots wont even take a tow out there if the thermals are not at least 500 fpm!