Forced Landing/No fuel

atsiii · #1 06-27-03, 07:00 PM

I am despondent to start this new thread, but if anything I say here helps you avoid making the same mistake I did… then the effort is worthwhile.

Last Sunday afternoon I ran my 1969 T337D out of gas about 8 minutes out from my home field. I elected to make a "wheels up" forced landing in a cow pasture. There were neither injuries nor damage to property on the ground, but my Skymaster (i.e. my love in life) is badly bent and possibly broken. As I walked around my bird in the field, I kept saying out loud and to myself… “I must have 12 more gallons… where is the gas… I had enough gas… where’s my 12 gallons?” How did this happen?

I have owned and flown my Skymaster for 4+ years, logging in excess of 1000 hours while enroute back and forth to 150+ airports in 35+ states and three countries. I would like to think that I’m pretty comfortable with its performance, limitations, systems, etc. I’d also like to think that I’m a pretty safe and proficient pilot. The truth is, I’m a pretty conservative (i.e. a sissy!) pilot, and very anal when it comes flying, and the taking and keeping of various flight records.

For example, I record the Hobbs at start-up, Hobbs at departure, Hobbs at level, Hobbs at aux, Hobbs back to mains, Hobbs at shutdown, etc. Further, once level, I lean both engines using the lean-find function of my JPI EDM 760, then religiously record which cylinder peaked, the temperature of peak, the target cruise temperature of peak minus 75 degrees, and the GPH fuel flow that results from running at 75 degrees rich of peak.

Because of all this, I am typically able to land and immediately calculate how much fuel I burned (i.e. how many gallons they will put on when they top off the tanks). For example, I might land after a 4-hour leg, figure I burned 98 gallons enroute, and then the FBO would pump on 101 gallons. I would think to myself, “gee, 3 gallons off over 4 hours! Not bad… 3 gallons off over 101 gallons, or a 3% error. Pretty darn close when you consider I still have in excess of an hour of fuel in reserve, or 20% more!” Thus, I have been struggling enormously since last Sunday afternoon, trying desperately to understand just how this could have happened. Well, yesterday afternoon I finally figured it out.

For the last 4+ years and 1000+ hours, my typical flight profile was point-to-point cross-country flying. I would fly 3 or 4 hours, land and top off the tanks, then fly 3 or 4 hours more. My time & burn fuel planning would seemingly always put me within 2 to 4 gallons of the actual gas purchased. So I developed a lot of confidence in the fact that I had 4+ hours of flying in my topped main tanks, and another 1.3 hours in my aux tanks.

The problem, as it turns out, is that I was not off “3 gallons over 4 hours” or “3 gallons over 101 gallons;” I was off because I was underestimating the fuel consumed during start-up, warm-up, taxi and initial departure (i.e. the fuel used before the weight was off my nose wheel squat switch allowing the hobbs to start tracking time). I had developed and was using a value of 6.62 gallons for this phase, but the real number now seems much closer to 10 gallons for my T337D. That was the 3 gallons my calculations were off over the years, and it all had to do with the period before the Hobbs meter started turning. But since my normal flight profile consisted of a 3 or 4-hour cross-country trip between top offs, there was only one cycle (i.e. start-up to rotate segment) per leg, and the 3 gallons was insignificant to the overall flight. Unfortunately, between 6/20 and 6/22, I had four separate start-up and landing cycles all on the same main tanks!

I wanted to attend a friend's wedding at Johnson Creek, Idaho (3U2). However, this is a 3500-foot grass strip in the mountains at 5100 MSL, with a blind S-curve approach to Rw 17 and tall pine trees at both ends. I had never landed my Skymaster on a grass strip; and I was a bit worried about my takeoff roll in long, wet grass. I also knew many of my pilot friends from U59 would be there, so in my typical (sissy!) fashion, I decided to fly over a couple of days and make sure I felt comfortable. I topped off all four tanks on 6/20 (128 usable) and headed over.

It was 1.5 hours over (hobbs), of which I flew 1.2 hours on my aux tanks. I landed, shut down and walked around a bit. What a BEAUTIFUL place to go plane camping! I started up, departed and flew home on the mains, which was 1.7 hours. Thus, when I got home on 6/20, I had put 2 hours on the mains and 1.2 on the aux tanks. I knew I would be heavier with all the camping gear on the 21st, so I elected to top off only my aux tanks. Just as expected, they put 24.6 gallons into the aux tanks (I had flown 1.2 hours at 20.7 GPH). I figured we would depart on the 21st with 1.3 hours of fuel in the aux tanks, and another 2 hours of fuel in the mains, for the 1.5-hour trip over to Johnson Creek.

On the 21st, I purposely flew most of the trip on the aux tanks (the POH requires all takeoffs and landings to be accomplished on the mains). Our time over was again 1.5 hours, of which I flew 1.2 hours on the aux tanks. We pulled .3 hours out of the mains, but .2 of those hours were in descent into 3U2 at 6 to 8 GPH fuel flow. Thus, once we shut down, I estimated we had about 1-¾ hours of fuel remaining in the mains.

As expected, Sunday greeted us with rain and lots of low-lying scud clouds. The weather began to break around noon, and was good VFR by 1pm. We loaded up our gear and departed about 2pm. Thinking (based on time & burn) that we had about 1 ¾ hours of fuel at takeoff, the plan was to climb VFR until we could see the weather to the east, then depending on how much we had to skirt around the clouds, we would land at Challis or Salmon for fuel before heading home. Unfortunately (as it turns out!), when we departed, we were handed a stairway to heaven VFR climb to the east right on up to 13,500, where we leveled off on top of a scattered to broken layer. Once we had leveled, reduced power to about 60% (27”, 2250rpm and 11.5 GPH), the GPS and Loran were both indicating 190kts groundspeed, and that home was only 58 minutes away. Since Challis and Salmon would require dropping down through some VFR holes, and since we were showing only .2 hours into the flight, and since I figured we had 1.75 hours of fuel at takeoff (of which we had used only .2), I reasoned that we could make the 1.0 hour trip home with a ½ hour of fuel in reserve. If the speeds didn’t hold up, we could stop at Idaho Falls or Rexburg. Well, the speeds did hold up, and even increased some. At one point we were 35 minutes into the flight, with only 30 minutes remaining.

About 12 minutes from the airport we started loosing engines to fuel starvation, and by about 8 minutes out, we had burned the last of the aux tanks, tried cross-feeding the mains, and were without any power. I feathered both props and we began looking for a forced landing site.

The Hobbs read 1.2 hours into the flight as we sat in the field. 1.2 hours… when I had departed with 1.75 hours… how could that be? Furthermore, we were out of fuel after only 3.7 hours of flight on the mains… when I had gotten 4+ hours of flying out of the mains since owning the airplane. What was going on?

I kept asking myself… “How do you put 6.5 hours of fuel on board for at most 6 hours of flying, then run out after only 5.7 hours. Well, hopefully my screw-up is now obvious to you all. I had underestimated the start-up to rotate fuel consumption by about 3 gallons. In my normal flying, that didn’t matter much. But in this case, I had 4 separate start-up, takeoff and landing cycles on the same tanks. I was off in my fuel estimate by 3 gallons after the first cycle… 6 after the second… 9 after the third… and 12 gallons (in excess of an hour of cruise!!) by the time I made my in-flight decision to head home on a 1 hour direct flight.

Folks… I don’t need a bunch of pilot jeering to rub salt in my wounds, and to point out everything I did wrong. I’ve probably already done a better job of that than any of you could, as I’ve always been my own worst critic. So please just think about this. All of us fly Cessna’s with worthless fuel gauges, so none of us rely on them. Most of us use one method or another of time & burn fuel planning. Please realize that if your normal flight profile changes, your normal (time proven!) rule of thumb may not apply! Sure, I knew I used more fuel on departure and climb… but I have all those values figured into my method, and I’m dead on with them. I've done the arithmetic, time and again. But I failed to realize I was underestimating the fuel used from start-up to departure rotation. Had I known this was closer to 10 gallons than 7 gallons, my arithmetic would have shown me I was cutting it too close (for a sissy!), and I would have put on more fuel.

I’m not sure what will happen to my beloved Skymaster. I am sure the FAA and NTSB will probably have a field day with me! But I needed to understand what happened, and I needed to share it before someone else made the same mistake. Think about what I did wrong. Think about adding a component to your fuel planning to allow for takeoff cycles. Think about developing graduated dipsticks for your tanks, and then using them before every leg. Nothing else can tell you how much fuel you really have. And think about getting a Totalizer of some sort, if you don’t already have one.

We walked away without a scratch having provided great entertainment for the cows and horses. But my Skymaster did not! Nor did my pride, nor probably my record. Please think about it. Fly safe!

Allen
N86182

kevin · #2 06-27-03, 07:28 PM

Thank you for sharing your story with us Allen. I am very glad you were not injured. Airplanes can be replaced. My condolences on the damage to or loss of your airplane.

With your permission, I would like to post your story on our site in the articles area, so that it will get the widest readership possible. I am sad to say that this is the second time I have heard a story like this relating to Skymasters, with the same result. Many pilots are not aware of how much fuel the startup/taxi/takeoff and climb cycle uses.

Again, thanks for your well written story, and good luck replacing your bird.

Kevin

atsiii · #3 06-27-03, 08:02 PM

I don't mind... but let me fix it first and I'll send you the Word document. I mis-wrote where the 3 gallon allocation is needed with my airplane... I said that I had allowed approximately 6.62 gallons and it is now obviously closer to 10. I meant to say that I had allowed about 2 gallons for that segment and it turns out it is closer to 5 gallons.

I'll fix the numbers and send you the Word document. Sorry, I was looking at too many numbers on my desk.

If the insurance company totals my plane, I may need to talk to you more about yours. If I have to replace mine... I think I will do so with a "P" and not another "T".

Allen

atsiii · #4 06-27-03, 08:43 PM

Kevin,

Here is the corrected Word document. I hope it helps someone.

kevin · #5 06-27-03, 10:58 PM

Thanks Allen. I will post it in the next couple of weeks.

Kevin

Bob Cook · #6 06-28-03, 07:46 AM

Allen

Did you confirm the amount of fuel remaining in either the mains or the auxs ?

I think this is critical for evaluative purposes.

Secondly, do you remember how soon the second engine failed ?

Did you play with the fuel selectors immediately after failure of the first engine?

Did you try switching tanks and running the boost pump after the first engine failed?

Your discrepency in fuel qty is about TEN percent. Does this include the non useable portion? I am not sure about your particular model but there should be a placard indicating minimum for takeoff and the POH should have this figure. I do not recall you taking this into account.

If 767 pilots can run out of fuel then it certainly easier for us GA people to do it. It only takes ONCE. I am glad to see you are skilled at zero thrust landings. As Kevin says aeroplanes can be fixed. It is a bummer to be without you bird.....

I feel there are more fuel outages in 337s than most other aircraft! I think it really important to actually determine balance of fuel in the aircraft after the forced landing if you have not done so.

IMHO The guages on the 337 are rather useless. I tend to rely on the Shadin fuel flow and would recommend this instrument is mandatory on all aircraft.

Bob

Kevin McDole · #7 06-28-03, 03:20 PM

Quote:

IMHO The gauges on the 337 are rather useless. I tend to rely on the Shadin fuel flow and would recommend this instrument is mandatory on all aircraft.

I concur. The fuel level and fuel flow gauges are very poor – and a totalizer is a great aid for fuel management. However, everyone needs to keep in mind that even with this equipment there are some ways to get fooled. These devices only count how much fuel goes into the engine – not how much you have in your tanks. It simply takes whatever you tell it, and does the math.

1) People do steal fuel from airplanes. The high octane AV fuel is attractive to street racers. Maybe your home airport has no security problems, but what about the various airports you visit for overnight stops?

2) I've had an aircraft parked on a hill lose 25 gallons out the vent tube. I filled it at night, and could see the huge stain on the ground the next morning. Also, the fuel level gauge did not show full anymore. I topped it off and was shocked to find it took 25 gallons.

3) I have had a fuel transducer fail in an intermittent way. Momentarily, the GPH would drop to 0. This would result in an undercount of the consumed fuel. Fortunately, I visually caught this.

The Shadin is a great product. JPI & EI offer these instruments too. Don’t blindly believe anything. Always cross check with whatever redundant info is available. On each fill up, confirm the quantities look correct. And on those overnight stays, treat the estimated fuel remaining with suspicion.

Bob Cook · #8 06-29-03, 08:05 AM

Kevin

Agreed. Last winter I had a coupling start to leak on the starboard tank when the OAT was -25. I only caught it because of the stain along the trailing edge of the wing. LOST about 5-6 gallons that did not show up on the Shadin. I caught it on the refeuling discrepency between the pump and the shadin total. I do monitor fuel on both tanks individually.

Another time the gascolator seal was leaking and didn't catch the loss on it until I saw it on the hanger floor. Loss... ??

There was a fatal accident in 99 or early 2k in Tennessee attributed to fuel theft.

When travelling in the Bahamas I carry tape (bright red) with me and put it across the oil door, fuel door and check for tampering.

My guages appear to be accurate when fuel is below 20 gal / side. Suggest you track the guages with the fuel depletion. You still need to cross check using fuel flow, time and consumption to feel comfortable. I consider my tanks empty at 8 gal / side.

You are right.. there are ways of losing fuel without realizing it. There is little question to quantity after filling the tanks!

The "P" is so much earier since there are no aux tanks.

just some comments...........

Bob

Ernie Martin · #9 06-29-03, 03:08 PM

How wonderful and gutsy for Allen to share this story with us. We are all in your debt.

In my "backup" 337 website at www.SkymasterUS.com the most important page is clearly the Fuel Management page. While it covers mostly 337's with separate auxiliary tanks (like Allen's), elements of it are applicable to ALL Skymasters, and it should be required reading for all Skymaster pilots.

I will share here what may be the most important practice that I use. I have one of those clear fuel dipsticks that you calibrate for your aircraft, so I know how much fuel I have by visually checking, including how much fuel I have when the dipstick is barely above zero (namely, when you can just see a tad of fuel under the opening). Well, my practice is that I never take off unless I have visually checked that I have at least that much fuel, and that it's at least one hour more than what I'll need. Had Allen done that on his last flight he would not have to write aqbout this.

We're glad you're safe.

Ernie

Jim Rainer · #10 06-29-03, 05:13 PM

Funny. I just tried to order a Shadin unit for my '76 337G to be installed at the annual about to start. They are 4 to 6 weeks out on delivery, so I didn't order.

The dipstick method may work on the plane with aux tanks but not on the ones, like mine, that have the 148 gallon tanks with only two fuel doors (on the high side of the wing.) Because of the dihedral, the fuel drops out of sight pretty quickly and a dipstick is useless, especially when fuel is preciously low. My gauges are pretty useless except when very close to dead empty when you can't get them to move no matter how much slipping and skidding you do to see if they'll register any fuel. I've spent a lot fo money trying to correct them but it's difficult to get them properly calibrated.

I have a fuel burn rule very similar to Allen but with more margin built in (remember I have over 7 hours of fuel at cruise.) I almost always top it off to have a known quantity at some point then use very conservative (on the high side) consumption numbers. Except when I have had it locked in my T-Hangar, I am always suspect of theft or leakage (Shadin no good here either.)

Over 4 years (but not nearly as many hours as Allen) I have developed a fuel burn estimate that usually results in less fuel needed than I had estimated. If I do a series of short flights, down low and several take-offs and landings, I add even more consumption.

None of this is to fault Allen. He's been much more scientific about his bird than I have mine.

The prevous owner of my bird was a partnership of pilots for a major cargo airline and I bought the plane only because one of them had run it dry a few miles from a nice airport, sightseeing down low with his little girl. Not much damage (landed ina soybean field gear-up) and no injuries, thank goodness.

stackj · #11 06-29-03, 08:10 PM

I still use the full tank/full bladder method...

6 hour fuel range

3 hour bladder range

WebMaster · #12 06-29-03, 08:41 PM

Sorry to hear of your loss, Alan.
Jim, your approach wouldn't have worked in this instance, because he didn't start with full tanks.

Guy Paris · #13 06-30-03, 01:29 AM

Sorry to hear that Allan, surprisingly my gauges are some what accurate. I don’t normally top it off after every flight because of the weight factor carrying all that fuel, 148 gallons I feel is not necessary. What I do is keep as accurate a log as I can, recording Hobbs time in and out and Shadin readings in and out. I will periodically, maybe 6 or so flights top it off to see how accurate things have been and in between add fuel for the given mission. I like to have 4 to 5 hours of fuel on board for the 100.00 hamburger, visit the grand kids, fly ins etc. It consistently uses 22 gallons per Hobbs hour. The Shadin has always come out telling me that I have used more fuel than I have, but only a small percentage. I also keep her in a locked hangar. I like Bobs idea of the red tape when away from the locked hangar...
Guy, the old 72driver.... that beast would use on average 10,000 pounds per hour.

Paul Sharp · #14 06-30-03, 01:29 PM

Allan, sorry to hear about your incident. But for the grace of God...

In recent years I have kept 7 gals. in each of my two aux. tanks. That way if I screw up somehow I know I still have a half-hour of flying I can get out of a switch of the valves. Sometimes for a long flight when I've topped everything off I've then run the aux. tanks dry so that I can refill them again on the ground back to the 7 gals., so it's not a foolproof scheme (as if there were something like that anyway). But I'm hoping it will save me an embarrassing day should it occur that I have to rely on the aux. "backup" at the unexpected sound of silence.

Dale Campbell · #15 06-30-03, 02:46 PM

Sorry to hear about your 337, but you did walk away. That is the main thing. I believe in Murrfy's law. So I leave not less than 35-40 gal before fueling up, in my 337H that holds 150 gal. total. I have had leaks in both inboard tanks & I do have shadin fuel flow meter, but it is just that, it helps control & meter fuel flow but is not a true gage for what is in the tanks. I use it as a guide to see if I lost any fuel between fill ups. In summer I try to keep my tanks around 80-100 gal., In winter I try to keep them full so I keep out condinsation. When you burn 22 gal/hr cruise & that extra on take-off, it goes fast. I also trust no one to fuel my plane, I watch them like a hawk or do it my self.