An Eclectic Mind

High density altitude with heavy ship.

During our ferry flight from Seattle, WA to Page, AZ, we decided to make a fuel/lunch stop at Bryce Canyon airport (BCE). Although I think we could have made it to Page with the fuel we had on board — about 1/3 tanks or 18 gallons to go 60 miles — we’d barely make our legal requirement of 20 minutes of reserve fuel for the flight. We’d also be flying direct over relatively hostile yet strikingly beautiful desert terrain. Not the kind of place you want to make an emergency landing prompted by a low-fuel light.

Bryce Canyon Airport is at 7590 feet MSL. We listened to the AWOS as we approached and learned that the temperatures were in the 80s (can’t remember exactly) and the density altitude was 9400 feet. (Whoa.) There was a 4-6 knot wind coming from the north.

Louis, a sea-level pilot, was at the controls. I figured we weighed about 2300 lbs. I knew we could hover at 6300 feet/104°F at max gross weight. Although I could have pulled out the manual to double-check the performance charts for our exact combination of weight, altitude, and temperature, I didn’t think it was necessary. After all, the 6300 feet/104°F combination equaled almost 11,000 feet density altitude (consult the chart; you can click it to see a larger view on Wikipedia). 9400 feet was well within that.

And Louis did well on approach. Although he came in a little fast at the beginning, he had a good approach speed and angle — at least by my standards — as we flew into the wind for landing direct to the ramp. He even got it into a hover where we’d park. But then the low rotor RPM horn went off. The helicopter wasn’t generating enough power to keep the blades spinning at the required RPM.

We were about three feet off the ground when this happened, so it wasn’t a big deal. I told Louis to just put it down. He was either fixated on the RPM gauge or trying hard to put it down gently, because he didn’t set it right down. He drifted backwards a few feet as we descended with the horn blaring. Finally, he put it on the ground. The rotor RPM shot up, but didn’t overspeed into redline.

I should make a few things clear here, especially for non-pilots, non-helicopter pilots, and non-Robinson pilots.

• Rotor RPM is life. If your rotors slow beyond what’s necessary for lift, the helicopter will indeed drop like a brick. That’s a very bad thing.
• The emergency procedure for low rotor rpm is to lower the collective and increase the throttle. We’re trained to do this so much that it becomes automatic. But lowering the collective isn’t always practical. The pilot needs to evaluate the entire situation — primarily height from the ground or obstacles (how close are you?) and rotor RPM (how low is it?) — before taking action. You don’t, for example, want to simply lower the collective if you’re at 95% RPM 3 feet off the ground in rough terrain at 2,000 feet density altitude. (Of course, you’re not likely to get a low rotor horn in that situation anyway.)
• Most modern helicopters have electronic governors that work with the throttle to make sure the engine delivers enough power to keep the blades spinning within an acceptable range of rotor speeds. My helicopter has such a feature. It works very well — except in high density altitude situations when the collective is raised quickly. Then it doesn’t always keep up rotor demand. In those situations, it doesn’t fail — it just doesn’t always spin the blades at the ideal 102% speed.
• On a Robinson helicopter, the low rotor RPM warning system, which consists of a loud horn and a light, kicks in at 97% RPM. That’s really high and it gives the pilot plenty of time to fix the problem before it becomes very serious.
• A Robinson helicopter can fly at 80% RPM + 1% per 1000 feet of density altitude. That means we could fly, in this situation, with 89.4% RPM. It isn’t recommended, but with a good pilot at the controls, it is theoretically possible.

The horn at landing had me concerned. After all, I was at the airport to have lunch and add fuel — both of which would add weight to the aircraft. (Okay, so lunch wouldn’t add that much weight.) If I couldn’t get it flying with what we had on board, adding fuel would only make matters worse. It was midday, after all, and we’d have to wait hours before the temperature started to drop. There was a chance we could get stuck there for a while. In that case, I wanted to know before I went to lunch so we could do something interesting in the park rather than sit around the airport terminal.

So I took the controls, bought everything back up to 102% RPM, and started raising the collective. I’ve done a lot of flying in high density altitude situations, so I know from experience that it takes a certain “touch” to avoid low rotor situations. I pulled the collective up slowly, felt the helicopter get light on its skids, and kept pulling. We were off the ground at 22 inches of manifold pressure, in a nice, steady hover. The engine sounded good, the low rotor RPM horn kept quiet. Keeping in mind that it takes more power to hover than to fly, I was satisfied that I’d be able to take off at our current weight and density altitude situation. I set it back down and we shut down.

But when I placed my fuel order, I asked for only 5 gallons. That’s 30 lbs of 100LL.

The line guy at the airport told us about how he liked watching the R22s take off from the airport. He said they only come in the late fall and early spring. They almost always do running takeoffs. I kind of wondered why they’d come at all. That helicopter, with two people on board, simply does not perform well at high density altitude.

We went to Ruby’s Inn on the free shuttle they offer from the airport. Three other folks who’d come in from Scottsdale in a small plane joined us for the ride. We had lunch in the restaurant there, ordering from the menu rather than waiting on line for the buffet. I had salad. I’m trying to lose weight and this seemed like a good time to stay on my diet.

After wandering around the huge “General Store” there, we hitched a ride back to the airport on the shuttle. I paid for my fuel, stopped in the restroom, and headed outside.

I admit that I was a little nervous about our departure from Bryce. One of the reasons for this was a recent R44 accident in Washington State that involved Louis’s old flight instructor. She’d been flying a Raven I in the Snowqualmie Pass area with three passengers on board when she’d crashed on takeoff. The NTSB report is still preliminary as I write this, but most folks are pretty certain that density altitude played a part in this fatal crash.

I’d wanted to depart into the wind, using the 6 to 8 mph breeze to help me get through effective translational lift (ETL), which occurs around 24 knot airspeed in an R44. The trouble was, the wind was blowing across the ramp area and a small jet was parked at the edge of the ramp, making a low-level obstruction there. If I hover-taxied over to the taxiway, I could takeoff downhill, but with a quartering tailwind that would not help the situation. Of course, a running takeoff — that’s where you get the helicopter light on its skids and run on the skid shoes until you’re through ETL — would be possible on the taxiway, which was smooth. In the end, I decided to pick it up into a hover and take off with a quartering headwind toward the runway and big empty space beyond its approach end. I’d have pavement under me for at least 200 feet, so I could always slide along it or abort the takeoff with a running landing if I couldn’t get enough lift to clear the fence and the road beyond it. You can see all this in the diagram; we were the red X.

I started up and we listened to the AWOS. Density altitude was now 9900 feet. (I guess it had warmed up a bit because there hadn’t been earth-shifting earthquakes while we ate.) Mike and Louis were quiet as I pulled pitch and brought the helicopter into a hover. I’m not sure if they were as surprised as I was that we didn’t get a low rotor horn. I pointed the helicopter in the direction I wanted to go, pushed the cyclic forward gently, and started my takeoff run. We varied from 3 to 8 feet off the ground before I felt the familiar vibrations of ETL. Then we were climbing nicely, well clear of the fence and the road. No horn.

I turned to the southeast toward Page and flew for a while before handing the controls back to Louis.

Landing at San Luis Obispo.

For my first Airport Codes meme entry, I thought I’d cover one that’s relatively fresh in my mind: San Luis Obispo (SBP).

SBP was a fuel and lunch stop on a flight from Wickenburg, AZ (E25) to Boeing Field (BFI) in Seattle, WA in May 2008. I was flying with Louis, a CFI who wanted to build time in an R44. Or maybe I should say Louis was flying with me, since he was acting as PIC.

Our arrangement was for Louis to fly and me to handle radio communications. We’d come in from the east, passing over Grapevine and climbing up trough the wide valley west of there. About 30 miles out, we broke away from the road and made a beeline to the airport.

I tuned in the radio, listened to the ATIS recording, and waited until we were closer to make my call. The female controller was issuing instructions to other aircraft. The airport wasn’t very busy for a late Saturday morning, but the radio was full of sound. The controller was chatty, which is extremely unusual for a controller of either gender. Either she liked to give instructions or she assumed the pilots were dumb enough to need as much information as she could provide. When I made the call about seven miles out, I made myself a target for her communications.

Oddly enough, I happen to have video for this flight. I had the POV.1 camera on the nose of the helicopter and although I didn’t realize it, it had been turned on since just past Grapevine. So you can see and hear the landing — including the chatty controller — for yourself.

In reviewing this video, I really think the controller had a bit too much to say. When a controller talks too much, he or she makes it difficult for pilots to make contact with the tower. Imagine, for a moment, that you were inbound to SBP and needed to establish communication with this Class Delta tower. There aren’t too many opportunities to talk during the 6 or so minutes from the time I first called in to the time we landed. This makes it tough, especially for new pilots who may already struggle with communications.

Anyway, we landed in the No Parking zone as instructed, cooled down, and shut down. Then we went up to the terminal area where there was a restaurant. After being completely ignored for about 10 minutes, we finally got an apologetic waiter. Lunch was good.

While we sat there, four airliners came or went. Let’s see if I can remember…American, US Air, United, and Delta? All of them were turboprops except United, which came in with a small jet.

After lunch, we went down to the ramp. Our choices for fuel were full serve, right where we were parked (A on the diagram below), or self-serve, on the other side of the airport (B on the diagram below). Self serve was 50¢/gallon cheaper. I made the wrong decision: I decided to air taxi to the other side of the airport and fill up at self serve.

In a perfect world, this would not have been a bad decision. In a perfect world, we would have started up, got immediate clearance to cross the runway, landed in front of the pump, shut down, fueled, started back up, and got immediate clearance to depart to the northwest.

But there was no perfect world at SBP that day. As we prepared to reposition, a flight of three or four Howards called in on approach. The controller, now a man, was having trouble keeping track of them, probably because they called in individually and they were all Howards. (Eventually, he just told half of them to stay clear of Class Delta.) With the other traffic part of the equation, the controller was overwhelmed. He wouldn’t clear us to cross the runway. So we sat there, spinning and sweating, waiting for the clearance. When we finally got it, I scooted us across. I was hot and cranky. I fueled up quickly and we climbed back aboard. I started up and we waited again. I called the tower three times and was ignored on the first two. On the third, the controller said, “Helicopter Zero-Mike-Lima, I hear you. Stand by.” Nasty.

By the time we left, I’d burned enough fuel to eat up any savings in fuel price. Lesson learned at SBP.

Read other posts in this series:

• Airport Codes: A Meme for Pilot Bloggers
• more to come…

What can you say about the airports you’ve landed at?

This afternoon, while slowly steaming in my camper with the air conditioner on full-blast, I took a moment to connect to the Internet, check my e-mail, and check up on my Twitter friends. One of them, Highway 89 Project photographer Ann Torrence, had linked to a blog post she’d just updated, “Collection of Airport Codes.” In it, she wrote about her dislike of flying and provided a table of codes for the airports she’s been to.

It’s interesting to me because the average person doesn’t pay much attention to the three- or four-character airport codes that are part of a pilot’s life. For each airport listed — and she listed airports all around the world — she included a very brief comment about her experience there.

While I’m not nearly as well-travelled as Ann, I’m pretty sure that I’ve been to more airports. In many cases, however, I was the pilot in command when I landed at the airport. I have my own story for each of the airports I’ve landed at. So I decided that it might make a good theme for future blog posts about flying.

This, in turn, triggered an idea for a meme — something that other pilots who blog could write about, too. What are the airports that you’ve landed at? Pick one and write about it. You can write about why you went there, what you were flying, or what it was like. You can write about the perfect weather or nasty crosswind or unreasonably hot temperatures. You can write about the coffee in the FBO, the courtesy car, or the line guy — or lack thereof. You can write about the people you were with and what they thought when you made that perfect landing — or two, or three. (Just teasing my airplane friends.)

If you pick up this meme and spread it, please do use the Comment link or form below to post a comment with the URL for the blog post you created. Be sure to say a little bit about the post when commenting to prevent my spam protection software from thinking it’s just spam and deleting it. (It tends to delete comments that contain only links, especially if there’s more than one link.) As long as the link points to a post in this meme as described here, it’ll stay. You can copy any part of this post to spread a description of the meme, as long as you link back to this post so others who follow it will add their links to the comments here.

In the meantime, I’ll start writing my own posts about some of the airports I’ve landed at. I’ll try to keep it interesting.

I hope those of you who have blogs will join the fun. Because, as we all know, an airport is far more than the three- or four-character code that represents it on charts, publications, and GPSes. I want to read your stories.