Month: November 2009

Last Week in the Forums: Check ride and alternator failures

A thread on VR this week about the alternator light is another example of why I’m doing this. In the R22 POH, the alternator light emergency procedure gets just a paragraph and is pretty straightforward: alternator switch off, non-essential equipment off, alternator switch on. Land as soon as practical if the light remains illuminated.

The thread on the forums this week started with a cracked drive belt, but moved into a discussion about the mechanical reasons the alternator light might become illuminated the grief that could cause you. In the POH, the primary concern is loss of electrical power, which would cause a failure of the governor and tachometer, and no way of regulating your MR RPMs. Even without an alternator, the battery should have 10-15 minutes of reserve power, allowing you to follow the procedure for landing as soon as practical (go to the nearest airport where repairs can be made). What isn’t in the POH is the risk of a loose alternator belt flying around the engine compartment. Once freed from the pulleys, it can become entangled in the drive belts, leading to their failure and an emergency autorotation. This is exactly what happened in a September 2007 accident. In this case, the first indication of a problem was the sound of the alternator belt breaking, followed by RPM instability. However, one of the posts on the VR thread suggested a scenario where an alternator light could indicate a failing alternator or alternator bearing, leading to failure of the belt itself. Even if the drive belts aren’t damaged, the belt that came loose in the 2007 accident contacted the oil cooler and lines. Conclusion? Consider making an emergency landing if the alternator light illuminates, and figure the problem out on the ground rather than in the air.

The other thread that was really interesting was about a pilot who failed his commercial ride. Basically, his instructor filled the tanks on the helicopter while the pilot was doing his ground portion of the check ride. He didn’t recalculate the W&B for the actual fuel load, and ended up 16 lbs over MGW. Shitty way to learn a lesson, but props to this guy for posting is story. I wonder if there’s an inherent complacency toward fuel because we do it so casually for our cars (except in Oregon and New Jersey!). Planning your fuel load is the first important step, but what got the pilot on his check ride was confirming what went in. Where I trained, we did the fueling ourselves, but I’ve been to plenty of airports where you touch down to refuel, and a truck comes bounding over to you. These guys aren’t going to attach the same importance you are of putting on exactly what you tell them. This job would be easier if you could always trust your fuel gauges or had a dipstick for exactly determining your fuel load. If you have the R22 weight and balance calculator and a smart phone with an Excel application (like Grid Magic), you can recalculate your fuel load right after you finish fueling.

A bigger problem that I’ve seen is not testing fuel for water or debris. Flying out of the same airport, you get to trusting your fuel source. Out in the real world–where you’re going to be flying from different locations, maybe getting fuel from barrels cached in the woods of North BFE–having a well entrained habit of always checking your sump might be a good idea. Since I learned to fly airplanes at an airport with a fuel service, I got into that habit. But another good reason is that things change, and you don’t always realize the implications. While working on my instrument rating, I started seeing rust particles popping up in the sump. This was after months of not having any indication of a problem. Turns out, the pump on the fuel truck was switched out while the original was being serviced, and that was the source.

Here’s another good one. Before you pulled the helicopter out of the hanger this morning, you checked the sumps and it looked good. It’s 10 degrees C outside and snowed last night, so you’re happy this will be a quick refuel–just 3 gallons. You drive the fuel truck from the tank out to the ramp, pick up the nozzle, pop it in the tank, and get your fuel. You know the truck is topped off every night, and you’ve never had debris or water come out of this tank. So, is there a good reason to check the sumps again? Anybody make a guess. Bueller? Bueller?

On an unrelated note, a couple of weeks ago, N74607, my favorite of all the R22 Beta IIs that I’ve flown, met it’s end in the Owyhee mountains. No injuries, and maybe it’ll fly again.

North Pacific Hurricanes

The North Pacific is a source for some pretty impressive low pressure systems. Stick them in the GOM, and they’d look like hurricanes. The one that blew in thisOR-Winds week had a pressure below 1000 mb and winds in the 40-60 knot range, which rivals a category 1 hurricane. The difference, I suppose, is that the warm waters of the GOM produce convective activity that strengthens the low, but this source of energy is missing in the higher latitudes of the Pacific. This storm caused some problems on the coast, but the winds dissipated pretty quickly.

What I wanted to point out about this particular system was the correlation between the pressure gradients and the winds. In this overlay of the SFC Prognostic Chart and the Wind Streamlines, you can see the low in the upper left corner, off the Washington coastline. Just southeast of the low the isobars are stacked pretty close together, but spread out as you move south along the coastline. The wind streamlines reflect the effect this has on wind speeds: southeast of the low, right where the isobars are stacked, the winds peak at hurricane force. North and south of the low, the winds meander around and peter out as the pressure gradient–the distance between the isobars–dissipates.

Do you know what the hatched area that stretches from central Mexico, through Utah and all the way up the west coast on the Wind Streamlines graphic is? Here’s a hint: the wind streamlines image I used was for the 3000 MSL level.

Downwash Lesson Plan

A couple of days ago, Tim McAdams posted on his blog, AOPA Hover Power, a couple of examples where pilots have been oblivious to the effect their downwash has on other aircraft. He warns that many pilots either don’t know about the effect their downwash can have on aircraft or personnel on the ground, or they don’t care. The AIM specifically puts the responsibility and discretion on helicopter pilots when judging the effects of downwash on persons and property on the surface (4-3-17(a)(3)). That’s the rationale behind the new lesson plan I just added, Rotor Downwash. (Maria Langer has also written about an incident where another pilot…well, just read her story.)

I trained at a busy school, where there were usually 3 or more R22s on the apron, and occasionally a few R44s, and we were next to a crowded parking area and the fuel pumps. Although the extent of our formal training in managing (and anticipating) the effects of downwash was the one paragraph in the AIM, you learn pretty quickly to keep doors latched, cowlings secured, blades slightly out-of-line with the tail boom, and a hand on your cap when others are arriving or departing. We also frequently had to frequently dodge airplanes that were seemingly oblivious to the recommendations in the AIM.  With the unwitting cooperation of the plank drivers at that airport, I’ve done the experiment and can say that an R22 on approach probably isn’t going to overturn an RV or a 152.

A larger helicopter though, packs a bit of force. I was waiting for a lesson at a small FBO in Oregon a while back. It was an early summer day, with calm winds and clear skies. The operator had just landed a fire contract, and they were practicing long-lining with it on the taxiway. While I was waiting, the mechanic moved a Cessna high-wing out of the hangar to pull out another aircraft, and left it there without tie-downs or chocks. After a half hour, the UH-1 returned to the hangar and went about setting the bucket down so it could land. The rotor diameter on a UH-1 is about 50 fee and they were working a 100-ft longline, so the Cessna was now within the 3-2-1 area (see the new Lesson Plan). There was an oddly calm moment between when the Uh-1 settled into a high-hover and when the downwash hit us. That Cessna was on its way the second the downwash hit us, and made it 20 ft before the mechanic and I stopped it. The force of the downwash from an R22 isn’t much, but the UH-1 laid down an impressive gust. This scene replayed itself almost exactly the same the very next day–the mechanic didn’t chock the plane, the ground crew didn’t prep the area, and the pilot (who worked at the FBO), didn’t make a radio call to have somebody secure the little plane.

Go check out the Rotor Downwash Lesson Plan.

The R22 Power Check: It Sure Sounds Like a Great Idea

Every year since I’ve been watching the Vertical Reference forums, there has been an “R22 Power Check” thread that pops up. When I saw it come up last month, I thought it’d make a great lesson plan. The thread always gets lots of views, users will put a lot of work into writing their responses, and on the surface, it’s a pretty important topic, right? Now that I’ve spent a couple of hours going over 10+ pages of posts from Vertical Reference, I’m not so sure.

The idea, as I understand it, is that you want a way of checking whether you will have enough power to make an off-airport landing. I’m going to mull over the threads on this for a while longer, but lemme put out this scenario that I got on a check ride:

Bubba & Sons Company has a station on a 6200-ft mountaintop that needs to be serviced, and they’re on the phone wanting to know if you can take Bubba Jr up there in an R22 to do the work. At the airport (2450 MSL), it’s typical weather for the desert in the summer: calm winds, 30 C and rising, and CAVU. You’ve flown with Bubba Jr, and he’s at 210 lbs, plus 20 lbs of gear. The nearest fuel is a 50-minute flight from the station, and the weight and balance shows you need to be at MGW to have the fuel to legally complete the flight. Do you take the flight?

There aren’t any tricks to this question. I looked at the HOGE, fuel requirements, and weather, and declined the flight. The HOGE suggests that the flight can be done, but that’s making several assumptions about the flight–that the temperature won’t be any warmer than 30 C when I get there and that my fuel burn will be at least 10 gph–and quite possibly my abilities. At 200 hours of experience, I told the examiner I wouldn’t do it since it was too close to the limits of the aircraft’s performance, but that’d I’d be happy to send him on it or to take a Raven II. He nodded and said that the customer would accept the R44, then went on to grill me on aerodynamics.

Right here, right now, I don’t see anything to support the need for this type of power check if you have reviewed your performance limitations before the flight. Realistically, you know what elevations you’ll be working in, and from that you should know what your HOGE limits will be. The approach I’ve taken during training is to determine the limit for performance, and then apply a buffer to cover things you cannot anticipate (like humidity, winds calm, a confined area, or higher-than-expected temperatures at the landing site). Reasonable estimates for all of these can be made comfortably while at your desk, and you can reevaluate winds, fuel, and temperature onsite. As long as those are below your limits, you can make the landing. (Since I’ve flown mostly at elevations that top out around 5500 ft, I’ve always had at least a 1000-ft margin to work with. I’m not sure whether this is too conservative to be practical though.)

So, to apply this method to the case above without going on for too much longer, I can assume winds are going to be calm on the mountain and that it’ll still be warm when I get there–maybe 28 C. I can also estimate my fuel burn at 8 gph and determine what my weight will be when I arrive. I can’t do anything about my passenger’s weight, my fuel load (my limitation on reserve fuel is higher than the required 20 minutes), or the landing zone to tilt the odds in my favor. Knowing this, I can look at the charts and tell I’m not going to be comfortable with this scenario. But, I can do the flight first thing tomorrow a.m. when it’s 15 C cooler. By the charts, I get a HOGE that’s 750 feet higher than what I need. Or, if I get to the landing zone with anything less that 1340 lbs, I’ll have additional power to draw on. The odds are now stacked in my favor. If I get there and there’s a 10 knot wind or the temperature is 12 C…Bonus!

The other way of looking at it…and this is something that I’ve used on just about every flight…is to set a limit and stick to it. We’re going to go work on pinnacle landings today? Okay, temperature, weight after 30-minute fuel burn…we can sustain a HOGE below 6500 MSL. Don’t ask me to go into 7000-ft terrain to practice pinnacles. In fact, maybe I don’t want to be practicing pinnacles above 6250 MSL. I’m also going to control for lower-than-expected performance from the aircraft by checking my hover power before departure. Is it higher than what I would expect from this aircraft on this day? And as I’m approaching the landing zone, does the OAT gauge show a temperature near or below what I used to calculate my performance back at base? Where is my MAP throughout the approach? Am I nearing my MAP limit as I’m getting close to losing ETL? I should be clear that I’m not suggesting that a chart in a book is the be-all and end-all to figuring out if you have the performance to land. But that that chart, developed by a pilot more capable than most of us and under controlled circumstances, is one part of the ADM equation (dammit, there’s another post to do…).

Back to the threads. Forget for a second that I didn’t see a consensus method described for conducting the power check, and that there is no procedure for a power check given in the R22/R44 POH or Maneuver Guide, or any FAA publication. But in the threads, numbers get thrown around, such as, “If you have a power reserve of X inches in cruise/in the downwind/at minimum power speed/etc, you can make a vertical landing” or “If you have less than Y inches of power, you can only make a run-on landing.” These numbers come from a variety of sources, some possibly more credible than others, but again, they aren’t coming from RHC or the FAA. On top of that, when they start getting into differentiating between a normal landing, a run-on landing, and a no-hover landing, those would be indications that we’re operating very close to the edge of the envelope. At that point, the question isn’t “Can I do this?” but instead “Should I do this?” Or maybe it’s “I bet I can do this!” that necessitates the power check?

If I’m wrong, I hope somebody with more real-world and teaching experience will set me straight here. But isn’t this analogous to dealing with weather limitations? We know what we can legally fly in, but we should also know what we are trained to fly in, and we should set a further buffer so that if conditions get worse, we have an out. But the whole power check concept seems to be just like the “Let’s go take a look” mentality toward weather. Instead of knowing that the procedure is well within the limitations of our aircraft and our training, it’s like saying “Maybe we shouldn’t do this, but maybe we can.”

Two last things I’ll throw out here. First, there’s the “HOGE power check”, which is something along the lines of getting near your LZ, slowing into a HOGE, and figuring out if you can maintain it. I guess, if you really want to be sure and the LZ you are moving into doesn’t offer any good escape routes for a go-around, maybe this is fine. It does entail some risk, and you may not get a good answer from it if you do the power check under the safest conditions (eg, 1000′ AGL, where it will be cooler and windier). The second is a mountain flying technique that I’ll cover another time, where you make several very slow passes at the same elevation as your LZ. This is for dealing with poor escape routes, downdrafts, weather conditions you couldn’t anticipate prior to departure, and nasty landing zones; it’s also part of a 3-5 pass low reconnaissance. I’ve read about these techniques, but wasn’t taught them. They do seem applicable to real-world applications scenarios that entail a higher degree of risk than you would encounter as a low-time pilot. My thought is that they entail more risk than is appropriate for flight training, but I don’ t know.

Right now this is all just armchair musings–I would like to figure it out though. It’s either a training deficiency–all 3 of the VR threads were initiated by CFIs–or maybe it shouldn’t be part of what students are being taught. As mentioned in several of the posts on VR, most instructors and students can recite the procedure, but they can’t explain the rationale behind it or cite a source for it (other than their instructor). Think about that.