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.