Should you "stop the prop" for a forced landing?

One flying philosophy I believe in is the importance of knowing the characteristics of your aircraft inside and out so that should the unthinkable occur, you the pilot are well-prepared to handle the situation with the highest likelihood of a successful outcome.

The Mooney M20E Owner's Manual includes a chart depicting glide range, and suggested indicated airspeed for best glide at maximum gross weight. The chart depicts a glide ratio of 10.3:1 with the propeller windmilling, and 12.7:1 with the propeller stopped.

Ok, well hold on a second... First, how do you stop the prop? Second, is it worth it do gain that additional glide performance in a power loss situation? Third - lets say you lose power, but still have engine rotation, oil pressure, and the ability to control the prop: What is the glide ratio then?

These are questions I'd had in mind for some time. Yet, its very seldom anyone in primary or transition flight training discusses these issues. Several years ago, when I began to instruct I decided to conduct an experiment to answer some of these questions.

Before I go further, I want to emphasize that yes, I took a small risk in these tests: I intentionally shut down the engine of my airplane a few times. I'm not advocating that you go out and do this unless you know what you're doing. For each and every test I was a few miles from a long runway on a nice day. I practice power-off landings from downwind frequently, and KNOW I could land it, on a runway, if I had to. I care about my cylinders and took quite a bit of time at the top and bottom of each descent to cool/warm the engine in a controlled, healthy manner. On the other hand, if my engine ever quits over some tall mountains... I think I am better equipped!

First, lets discuss the experiment setup and conditions:

• Aircraft: 1966 Mooney M20E
• Lycoming IO-360 engine
• "Standard" Hartzell (non-schimitar) propeller
• Engine controls are rigged such that it idles about 750 rpm on the ground, prop full forward
• Atmosphere close to standard temperature
• Aircraft weight 80% of gross weight, with glide speed adjusted accordingly* to 95mph indicated airspeed

*The Mooney Owner's manual publishes a best glide speed of 107mph indicated airspeed, but says elsewhere that L/D max is 105mph indicated. Like all airspeeds that attempt to capture a desired angle of attack, best glide needs to be adjusted for any variance in aircraft weight versus the weight the speed was published for (max gross). I adjusted the 105 mph speed for actual weight, so the target speed was 95mph indicated. For further reading on the topic, Aerodynamics for Naval Aviators is a good reference.

Experiment method:

1. Established the aircraft in a power off descent slightly above 5000' MSL
2. Trimmed for target airspeed, allowed the aircraft to stabilize
3. Started a stopwatch descending through 5000' MSL
4. Measured time after 500 vertical feet of descent

Here were the test cases, and results:

So, what does it take to stop propeller rotation?
The method used was to establish a glide at idle cut-off, propeller windmilling, propeller control at "Max" RPM. I started a stopwatch once target glide speed established and stabilized. I simultaneously increased pitch to slow the prop. It took several seconds, at minimum control airspeed with slight stall buffet (a full stall was not necessary) to stop rotation. I then reduced pitch to regain calculated glide speed. At this point the elapsed time and altitude loss from starting the maneuver were noted: 25 seconds and 300 vertical feet.

Conclusions:

1. If I lose the engine and making a safe landing sight field is questionable, it is probably worth stopping the prop, provided that I did not have oil pressure to use the governor to do so. You can cover about 25% more ground with propeller rotation stopped vs. windmilling with the propeller control set to "Max" RPM. So its not a slam-dunk that will double how far you can go, but if the best option for a SAFE landing sight looks "iffy", I would, without question, stop the propeller
2. If oil pressure and propeller governing are available, the difference in performance between windmilling at "Min" RPM and the propeller stopped are quite small, about 10%; stopping the propeller may not be worth the additional distraction from dealing with the emergency
3. The Mooney owner's manual glide ratios appear very close to the data I captured
4. The effect of an idling engine on perceived glide performance is substantial. It does lend credit to the idea that when practicing this in a normal environment with the engine still running at idle power, that you do derive some benefit that will not be there in an actual emergency

Survival After the Forced Landing

Here's a presentation (and lecture notes) I put together and gave at my local airport recently on some ideas for improving your odds of surviving a forced landing. This was largely inspired by preparation of the Alaska trip featured earlier on this blog.
Survival After the Forced Landing

ADS-B receiver & iPad combo: Early Impressions

Now that you've read all about what ADS-B in and FIS-B are, here are some screen-captures and commentary of my early experiences using it. Also: One piece of reference material that may be interesting if you're still learning that I forgot earlier: AIM section 7-1-11.

The setup I'm using is an Apply iPad (first edition), the SkyRadar ADS-B receiver, and either SkyRadar's own iPad app, or the Hilton Software WingX application. Which app to use is probably best left up to you: Both are available for free trial. After that, WingX requires a subscription fee, and the SkyRadar app requires a fee to update charts, but appears to continue to work afterward for free for displaying the ADS-B data.

In subsequent posts I'll get into discussing traffic (through TIS-B), data coverage, and some of the other quirks I've noticed. This post is all about the FIS-B data you can receive and how each app handles it.

The executive summary on which app is better for the FIS-B data is a toss-up: Neither support 100% of the data being transmitted, which is unfortunate. They get the most important bits, with WingX getting the edge for my vote in terms of organization of weather data. Because of these limitations my plan is to use WingX as my primary charting and weather display app, but will keep the SkyRadar app installed in case I need data I might be missing.

Over the past couple of months I've flown several trips with the setup, which is where I got the screen captures below. Most of the time I ended up using WingX, and have subsequently paid for an annual subscription. I'm going to skip describing the core features of each app in favor of concentrating on the FIS-B data. The WingX folks have some pretty good video documentation describing their product which you may want to view before purchasing their app, and the SkyRadar folks PDF documentation you can download.

NEXRAD (weather radar) is downloaded in 'strips'. You can overlay radar on any of the chart types (i.e sectional, en route IFR, topographic, or a blank map where you can add other aviation layers like airspace, airways, etc. My preference was to overlay the radar on an en-route IFR chart. Areas where radar data has not been received (or are outdated) are slightly opaque, giving you a very clear picture of what radar data you have (or are missing).

Local NEXRAD granularity - WingX

En-route NEXRAD - WingX

 A few interesting observations about radar using this setup:

• High resolution "local" NEXRAD images are downloaded for approximately 200-250nm of your present position. The FAA says 250nm in the AIM. In practice I noticed a few opaque 'strips' toward the outer reaches. Based on this I'd say 200nm is a good safe range. This seems fine for the type of flying I do but folks flying faster (i..e turbine) aircraft may have a different impression. Then again, they are more likely to have on-board weather radar 

Local NEXRAD coverage on a clear day - WingX

• How old is that image, anyway? The WingX support folks who told me old data 'strips' were made opaque after 10 minutes. SkyRadar has the data's age printed right there on the screen -- but its not clear what that age means considering you could be looking at many strips of radar data at a time (i.e. if you zoom out a bit)

NEXRAD "strips" that were too old or not received. This usually corrected itself within a couple of minutes. Occurs in either app - WingX

• The AIM says the local NEXRAD data is broadcast on a 2.5-minute interval, with new data arriving into the FIS-B system every 5 minutes. By my math, an image you're looking at as valid on the screen could be 25 minutes old, worst-case (NEXRAD itself takes 5-10 minutes to produce an image). Needless to say, this is not a tool you'd want to use to tactically avoid convective weather or to try to make a run through a 'hole'

• A low resolution NEXRAD composite for the continental U.S. is transmitted on a slower interval (10 minutes). The SkyRadar iPad app displays it, but WingX doesn't just yet (12-March-2012: A new WingX update arrived which supports the long-range NEXRAD composite. I'll try it out next time I take my airplane up).

Low-res nationwide NEXRAD composite. Useful when you're zoomed way out - SkyRadar.

METARs & TAFs are downloaded within either a 100 or 500nm range, per the AIM. In practice I have seen METARs & TAFs consistently available for out to about 500nm away away from my position on every flight.

A nice thing about WingX is how it manages this data. You tap next to an airport (any airport), hit weather, and the METARs/TAFs/PIREPs (etc) are displayed with the closest to the station first and radiating out from there. This is simple and intuitive, and means rapidly getting at the information you want (how's the weather surrounding some point in space) without a lot of head-down time in the cockpit. I like that.

TAFs - WingX

METARs - WingX

With the SkyRadar app, you've got to scroll over each airport of interest to display its METAR and TAF (if they exist at that airport).


PIREPs are downloaded within a 500nm radius. I did a couple of tests to see how efficient the system is at disseminating a pilot report. Flying over the California/Arizona border going east, I gave a pilot report verbally to flight watch. It was mostly benign weather, so I reported a smooth ride and the calculated wind aloft. It never showed up on the ADS-B feed. When I looked for it online after landing, it wasn't found either - I can only assume the flight service guy never sent it in.

My PIREP - WingX

On the return trip a couple days later, I encountered some mountain wave in western New Mexico and gave a pilot report. My PIREP showed up on the ADS-B feed to the iPad about 5 minutes later. Very cool. Similarly, on a recent trip to southern California where I diverted for weather, the receiver picked up pilot reports of icing that were brand new, not present when I checked weather on the ground prior to takeoff not an hour before. That helped my decision making as the minimum IFR altitude in the area was right about where the icing PIREPs were.

Similar to METARs & TAFs above, the pilot reports in WingX are shown in order of distance radiating out from a particular station you're interested in. This is an area where the SkyRadar app is lacking; per their documentation you have to go hunting around for an icon next to an airport or VOR nearby to where a pilot made their report (this is per SkyRadar's literature; I never did see any in flight).

NOTAM (D & FDC), and TFRs are sent out with 100nm. That seems arbitrarily close, particularly for TFRs. Displaying NOTAMs is similar to METARs & TAFs above - scroll over an airport of interest with the SkyRadar app, or be given all of them radiating out from some airport using WingX.

Potential gotchas? WingX does not appear to currently support displaying TFR data, and it doesn't explicitly say if it supports FDC NOTAMs. This area is decidedly one where the SkyRadar app does better, pending further software development.

America's most bogus (Disneyland) TFR - SkyRadar

NOTAM-Ds - WingX

NOTAM "D" & "FDC" for Santa Maria - SkyRadar

AIRMETs are sent out within 500nm.WingX provides the AIRMET text in a similar, geographically oriented format when looking at weather for a particular airport. Surprisingly, I couldn't find any AIRMET data in the SkyRadar app, on a flight when there likely would have been one in the area for low ceilings/IFR.

AIRMETs - WingX

SIGMETs are transmitted within a 500nm radius as well, but neither SkyRadar nor WingX appear to support dissemination of these yet.

Winds & Temperatures aloft are sent within a 1000nm radius (so half of the lower 48, roughly). SkyRadar shows these nicely - just pan around an area and you'll see a table of forecast wind & temperature aloft data from the nearest forecast point. WingX does not currently support winds & temperatures aloft from the ADS-B receiver. It will show you winds from the last time you downloaded weather from the internet.

Winds & Temperature aloft data is shown from the last internet weather download - WingX

Special Use Airspace status is sent out within 500nm. This is another product that the SkyRadar app supports, but WingX does not. I had to hunt around to find a hot restricted area using the SkyRadar app. Frankly, its one area of the ADS-B feed I don't think I'll rely on regardless of software support. I want to hear ATC tell me that a particular restricted area is cold before entering. Whether VFR a pilot elects to fly through a hot MOA is a whole discussion and judgement call in itself, but again my preference is to ask ATC.

Special use airspace status - SkyRadar

Intro to ADS-B weather

I last visited Oshkosh in 2010 where I started taking an interest in ADS-B. If you're new to that acronym, you can read all about it here. The prospect of having to spend money on a new piece of equipment (ADS-B out) didn't excite me much, but that won't be required until 2020 anyway. ADS-B in, on the other hand, I found intriguing, particularly after another flight across the country with periodic calls to flight watch asking for a verbal description of weather ahead. That's because a subset of ADS-B in, FIS-B, allows pilots to receive weather data in the cockpit. This post discusses my experiences with FIS-B using portable electronics to receive and display weather information.

Weather in the cockpit has been available for some time through XM satellite data subscriptions, billed at a monthly fee. FIS-B in is free (more precisely, we're paying for it through FAA funding). You need a receiver and something to display the data on, though. The weather and other data services broadcast through ADS-B are discussed in the AIM (section 4-5-9, new as of 2011). I had previously seen XM weather in action while riding in other pilot friends' airplanes as well as with instructional clients, but decided against it due to the nature of my flying (sporadic long-distance trips - maybe one every couple months - where its really handy). Buying a receiver, and then having the data for free, was much more palatable in my case.

One of the fundamental limitations of ADS-B is that it is a ground-based system. You must be within line of sight of a ground station to receive the data. When I was learning about all of this in the summer of 2010, coverage was somewhat sparse, but transmitters were being installed in various locations throughout the country. Fast forward 18 months and the coverage was pretty good; you can see a map here (click "ADS-B" and then "radio stations"). Because ADS-B was now largely available in the western U.S, I decided it was time to give it a try. Note that large areas of the inter-mountain west are still without these stations.

Recall that 2010 was also the year the iPad was introduced, and its place in the cockpit was quickly taking root. Going to Oshkosh and back that year was the first big trip I'd taken using chart data on my iPad. There at Oshkosh I also came across the SkyRadar booth. Staffing the booth were the engineers who had built a portable ADS-B receiver, and integrated it with an iPad app, to display weather data in the cockpit.

After chatting with the SkyRadar guys a while I asked about what was inside, and was surprised to learn they were using technology I'd worked on professionally outside of aviation for the better part of the past decade. This is more of a source of personal pride than anything; I have not received any compensation from their use of this technology and do not anticipate it benefiting me financially in a material way in the future, but I felt compelled to disclose that.

With the technology coming into alignment, at a reasonable price, I decided a buy a SkyRadar receiver late last year and have now had the opportunity to use it on a couple of cross-country trips. I evaluated both the SkyRadar's own iPad app and WingX -- currently the only two iPad applications I'm aware of that will display data the receiver picks up. In subsequent posts I'll get into my experiences using the receiver on a few trips. Many screen-shots to come.

In the mean time, AvWeb has put together a pretty decent video comparing the SkyRadar ADS-B receiver and the WingX app (what I'm using) versus an XM weather receiver and ForeFllight:

Formation fun

With my Alaska trip written up I've come up with several ideas to keep this blog going. Some will be trip reports, some surrounding technical aspects of flying that have interested me enough to further my education on.

...but sometimes, you just have to go out and have fun. I've flown the San Francisco "Bay tour" many times. One day last year, several folks were visiting and a pilot friend and I decided to take them on a bay tour. Why not make it a flight of two? Here's a little clip one of the passengers took near Sausalito.


The sun had just set. Next time, we need to get up there before sunset to get the #2 airplane basking in that "golden hour" light outside the bridge. That was also the flight where I got the image that's presently at the top of this blog -- the sun was just above the horizon then, just past abeam SFO.

Formation flying is a fun challenge. Like many things in aviation, preparation is the key. We had a lengthy preflight brief going over our plan and several what-if-type scenarios. Flying the #2 airplane, I didn't enjoy much of a bay tour at all - my eyes were glued to the lead, who scanned for traffic, talked with ATC (we were treated as a single airplane), and the like. I'm by no means a formation expert but had some good training on it, along with aerobatic flying, shortly after receiving my private pilot license many years ago.

Alaska Epilogue

Before committing myself to fly to Alaska I wasn't sure if it was right for me, or worth the time and expense. Would it be better to use that time and money to travel to new faraway lands? To seek breadth in the mountains I'd already explored closer to home? Now, a month after returning home, my only regret is not having spent more time in the North, and I have a strong desire to go again. I've been fortunate enough in life to have seen a great deal of the western United States on the ground, in the air, to explore the Pacific coast from the tip of Baja to the Washington coastline, and do to a fair amount of international travel.... yet going a bit further north from home was surprisingly foreign and alluring, and I barely scratched the surface.

Trip route & places I landed.

If you've just found this blog, I'm writing up a diary of the trip, dating the posts as they were on each day of the journey. If you'd like to follow chronologically (i.e., not the way blogger will display them on its own), this list may be useful (not all the legs have been written up just yet!):

• So begins the northbound odyssey
• Seattle
• North to the Yukon
• North to the Yukon... the trench
• Weathered in Watson Lake
• Southeast Alaska attempts, and Whitehorse
• Wrangell St. Elias wonder, and Alaska, at last
• Marshes, moraines, mountains, and rain
• Mooney fun in Talkeetna, introduction to Anchorage
• On the ground in Anchorage
• Chugach hikes
• Seward & Exit Glacier
• Back in the air - IFR to Homer
• Heaven is spelled "Seldovia"
• Talkeetna Revisited
• Denali color
• Homeward Bound  
• Return to the lower 48
• Home again 

If you're considering making the trip as a first-timer, these may interest you:

• How to cross the U.S./Canadian border in an airplane
• Weather services for pilots in the North

Numbers:

• Aircraft: 1966 Mooney M20E
• Number of mechanical breakdowns or things that broke along the way: 0
• Flight time: About 40 hours in the air
• Distance: A bit over 5,100 nautical miles, round trip
• Least expensive avgas: Anchorage Merrill field, $5.09/gallon
• Most expensive: Whitehorse, Yukon, $8.40CDN/gallon
• Nights camping: 9; in hotels/B&Bs: 3; in hostels: 3; couch surfing: 2
• Cars rented: 3

Home again

Days 17-18: Portland, Oregon to Trinity Center, and Watsonville, California

The next day was spent with family in Portland. If there was any doubt about possible culture shock the evening before, today confirmed it beyond a shadow of a doubt. After walking off some outstanding German panckes for breakfast, we walked the Ladds addition and met two of my cousins, uncle and aunt, spouses, and a room full of little kids to catch up. We had a delightful lunch, hosted by my cousin's wife. The call of the wild at Watson Lake was faraway, indeed.

One last DeHavilland spotting, Starks Twin Oaks

Making our way back to PDX to turn in the car, I firmed up plans to take a college friend and his wife flying. We'd meet them at Starks Twin Oaks airpark, barely a 10 minute flight yet a world away from the concrete jungle of PDX. I decided to delay my takeoff a couple minutes for an arriving C-17 transport that landed in front of us due to wake turbulence. Twin Oaks, just south of Hillsboro, offered a laid back place to unload the airplane to accommodate two passengers for a quick flight around the countryside.

As we set up to leave Starks it was late afternoon. A quick call check weather at home (Watsonville, CA) revealed fog already close to minimums to fly an instrument approach and see the airport. The best approach we have, a localizer, allows a pilot to get down to about 600 feet above the ground, and the summertime fog that usually rolls in during the late evening is often below that.. By the time we got there, three-plus hours from now, there was almost no chance of making it in without a diversion. The summer of 2011 had been a pervasive one as far as the fog was concerned and it showed no signs of abating. For those unfamiliar, September, October, and November are usually the best months to visit the California coast, with the exception of 2011!).

With a diversion assured, it was now time to think of a plan B. I'd had one in the back of my mind already. Trinity Center, in the mountains west of Redding, offers the flyer a peaceful lakeside airport adjacent a warm reservoir of clean water, a peaceful place to camp, and a small community nearby. I'd stopped once before for the evening on a trip north out of curiosity rather than necessity and enjoyed it; I wanted my wife to have a look. There should be just enough daylight to get there by sunset, a necessity as the airport is unlit and in a mountainous area. Its a daytime-only field for sure.

Loaded and fueled once more, we departed for Trinity Center. In contrast to the clear skies over the Puget Sound the day before, there was now a fair amount of smoke from fires burning in the Cascades to deal with as we proceeded down the Willamette valley. It wasn't pretty down low, and the visibility was certainly questionable VFR from 8,000 to well over 11,000', and quite smelly as well. We finally got completely on top of the smoke around 12,000' and cruised south at 13,500' where the air was smooth and clear.

On almost every trip I take to or from the northwest, there is usually some kind of weather change around the California/Oregon border over the Siskiou mountains. This is usually where weather systems get ripped apart leaving California warm, and the Oregon mountains under cloud, precipitation, and icing aloft. Today, the weather was great, but just like magic, the smoke ended as we got to the Siskious. The familiar sights of Mt. Ashland where I'd learned how to ski, Mt. Shasta, Scott Valley, and finally the Trinity Alps greeted our return to California. I delayed descent over the mountains as the sun was now setting, electing to make a few circles over Trinity reservoir, adjacent the airport. We landed with perhaps another 10 minutes of light sufficient to land given the terrain and unlit field.

Pitching our tent in the fading twilight on the ramp next to a picnic table, an SUV drove onto the field. Inside was a gentleman who upheld Trinity Center's reputation as a very hospitable place to visit. He lived in a house further down the field and decided to drive over just to see if we needed anything. He ended up inviting us over for breakfast the next day. During my last visit to Trinity, a family was picking up their son who flew in about the same time as me. They returned in the evening to invite me for breakfast at their home. Here I was, for the second time, invited to a stranger's house for breakfast! Its hard to beat that. Our evening was pleasant - quiet, warm, and with a sky full of stars to feast upon.

The next morning, after a brief swim in the lake, we made our way to our new friend's house for breakfast. He was a retired M.D., who had previously owned several airplanes and had taken several trips to Alaska. Naturally, we had plenty in common to discuss.

"After I got back from Alaska, there was a medial convention in Brazil I was planning to attend", he remarked. "I told my father I was going to buy an airline ticket and he said 'Why not just fly down yourself? You just flew to Alaska and back'." So with that, he flew to Brazil, in the 1960s, in his twin-engine Piper.

After lingering a while we began our last leg of the trip. It seemed apropos to say goodbye to our new friend with a low approach down the runway, but a couple of crows circling near the runway's end kept me from descending as much as I would have otherwise. The way home was positively routine. Light wind, warm atmosphere, California sunshine...all the way to the fog-laden coast, anyway. The fog was just starting to break when we arrived. I requested an IFR clearance to fly a localizer approach, broke out, circled to land, and touched down nonchalantly, as if from any other flight in the local area.

We called my brother in law, who had graciously come to house-and-dog sit for us while working remotely, to pick us up. While waiting, my wife ran into a man I used to work with (outside of aviation) for several years. He had just come down to the airport at random to take a look.

"Where did you come from?" He asked. "Well", I said, "Alaska."