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There has been a significant discussion between AgAir Update readers about the proper way to execute an emergency dump. AgAir Update feels this topic is important enough to reproduce gainful information that is received from readers. The following is a recap of the dialogue. To contribute to this forum, please email your comments to aau@agairupdate.com. |
Emergency dump
I have four short “sea stories” to tell you. (I am FULL of sea stories, as are probably all of you old timers like me).
First sea story: A few days ago I bumped into a fellow ag pilot friend, Brandon Mulhearn. Brandon had an AT-802 at a paint shop in Texas getting a new paint job in order to comply with new regs which require that all SEAT aircraft be painted with the new red and white paint scheme, and then Brandon related the following:
As it was, Brandon’s pilot was sitting on the end of the runway in his AT-802 preparing for departure and the return flight to Louisiana, when he observed an ag plane make what appeared to be a practice spray pass down the runway. However, prior to making the spray run, the pilot abruptly broke off the pass, and dumped the load of water in his airplane. The airplane pitched up, stalled and impacted the ground before the pilot could recover resulting a fatality. I personally suspect the pilot INADVERTENTLY dumped the load because he obviously was not prepared for the sudden and violent nose pitch-up to the near vertical.
Before we parted, Brandon suggested that I may want to incorporate this information in our Turbine Transition Course, and maybe write about this topic in my AAU column. I thought his suggestion was a good one and, so I am.
Second sea story: About a year ago I was transitioning two pilots from Burkina Faso, Africa, into turbine ag planes. It was on our first flight with a load, 350 gallons of water, in the hopper of our S2R-T15DC. We entered the practice field from the east over tall trees. I had my right hand lightly touching the stick, as I always do. Over the crop, I said, “Spay on,” but to my shock and surprise, my student hit the dump handle. My left hand instantly joined the right to help push on that “fence post,” but to little avail. Out of reflex, terror and a major adrenaline rush (and on the screaming advice from my guardian angel), I rolled the airplane hard to the left. As soon the nose passed through the horizon, we were safely flying again. We promptly returned to the Rayville, LA airport and I hosed out the airplane’s back cockpit. Now that’s a joke, albeit a bad one.
Third sea story: a few years ago I used to do refresher flight training for the pilots of the Dole International Fresh Fruit Company in Costa Rica, Honduras and Ecuador in one of their S2R-T34DC Thrushes. The first flight was made with the chief pilot, Gilbert Gonzales, an exceptionally good pilot with the Costa Rica Division. We had almost 450 gallons in the airplane and once again, me in the back seat. On take off with max torque on the PT6-34 and approximately 10 feet in the air, I said, “DUMP,” which he did. Our preflight brief was to dump approximately half the load, but we jettisoned every tiny cubic centimeter. Once again, the Thrush tried to emulate a Saturn V at Cape Canaveral. With both of us pushing as hard as we could, one of us retarded the power lever and we both rolled the airplane to the left, ...and lived to tell about it.
Fourth sea story: several years ago, probably in the mid 70s, Henry Mounce was flying a Turbine Thrush out of Morgan City, MS. Entering the field on the first pass with a full load, Henry inadvertently (as they say) hit the dump handle. The pitch up was so violent that his backbone was compressed somewhat and Henry was grounded for several weeks.
IN MY OPINION, I think there are at least two morals to these sea stories, the first being to pay attention to where you put your hands (I am referring, of course, to the airplane). The second one is, if you dump a heavy load, deliberately or accidentally, be prepared to push very hard and roll the airplane either left of right. In our Flying Tiger Aviation Turbine Transition Course, I always include in the preflight brief that in event of an emergency dump, we agree to roll to the left (or right if a left turn is unsafe, etc.) if we cannot get the nose back down to the horizon. I’ve never seen this procedure published in any ag-plane flight manual, but I think it may be something for you to think about and maybe try it, but not with a full load. You must be sure you are slower than the published max dump speed, if there is one, otherwise you could over stress the airframe. If you’ve never done this before, it will get your attention. In our turbine transition course, we do practice dumping a partial load after spraying, but we slow to 100 mph, extend 5° of flaps and slightly lower the nose. There is still a pitch-up, but easily handled.
I want to say right here, I am not an aeronautical engineer, or an aircraft designer. Nor do I hold myself out as an expert in teaching proper response in all emergency situations. How-some-ever (that’s good southern English), in my own personal experiences, pushing hard on the stick and rolling the airplane with lots of rudder in the direction of the turn has ensured that the airplane could be returned safely to the original point of takeoff, intact. Keep in mind that the faster the airplane is flying when you dump, the greater the load factor (G forces). The severity of pitch up is primarily a function of airspeed and aft shift of the CG. We must also keep in mind that with me at 200 lbs, the immediate aft shift of the CG will be even more severe that any single seat ag plane.
IN MY OPINION, this dumping issue is something to consider and practice. If anyone has a comment, pro or con, regarding my ideas and procedures, please email me or aau@agairupdate.com I would love to hear it.
Be safe, have fun and make money.
Robert A. McCurdy
FLYING TIGER AVIATION, LLC
Chief Plot / Flight Instructor
Editor’s Note: Lin Stanton of Sunnyside Aero in Mississippi and I had an email discussion about the proper way to execute an emergency dump. The following is how it went:
Bill: I hope you are doing OK! I believe everyone got either an email from the NAAA, or a fax, last week. In it I read about practicing dumping.
One of the flight proficiency checks that the FAA use to do was watch the pilot dump a (small) load of water. I’m referring to back around the late 1970s.
Our shop always tries to make sure the dump works properly and checks it usually with enough water to make sure it is tight enough to not spring open on takeoff.
The old Ag-Cat I used to fly had a bar that was set with a screw jack to adjust the position of the bar to control the amount of dry material you wanted to apply. The screw jack (for lack of a better word) blocked the dump handle from going to far forward.
As for dumping water out of a turbine, you are not going to like dumping more than 100 gallons at cruise at any one time! When I use to change back and forth from dry to liquid several times a day, I taxied in from dry work, got 150 gallons of water, departed, and before the air speed got to 125 mph, with the flaps at 5° (and remember the dump handle is set for dry work and is easy to open) crack the gate open. From this experience using a small amount of water and the aircraft properly set up to dump, you know it would not be good to find yourself in a position as to dump 450 gallons all at one time. The 125-gallon dump was good for cleaning the spreader and the lower tail and belly fairly decent enough to change over and go to wet work.
I have only dumped one spray load (back when they were less costly) because of an engine failure, in a turn. I pulled the pin so as to be able to make an open field. It was in a 600 Ag-Cat.
Back to the beginning, and reason for this dissertation. In the Air Tractor, if you crank the solid gate setting wheel almost closed (maybe where the gate will only open about two inches), when you are flying liquid work this would be a safe setting for an emergency dump, or an inadvertent dump. You would still lose a large amount of liquid, but it wouldn’t go wide open on you in the middle of a emergency.
In closing, there are many corners we can put ourselves in this business of ag-aviation. We need all the help we can get. I truly think complacency gets more pilots than any one thing!
Lin Stanton
lws@i-55.com
Hi ya Lin;
Points well taken. I’m wondering, cause I never tried it, how the turbine aircraft would react at cruise using the max dump rate with a catastrophic power failure, as usually it will be with a turbine. At that point, since you no longer had any power and the airspeed dimensioning very rapidly, could you get away with a full dump? I’d be concerned the one to two-inch opening might not be fast enough to clear the trees (no power and pulling up). I know it’s almost impossible to get the stop lever out of the way if you needed to go to full dump.
There’s no easy answer. Do you set up your aircraft to risk a slow dump or go for the max dump? Just my thoughts. —Bill
Bill;
Yes, I do see a need for a controlled dump setting. You are checking a lot of things all at once when the decision to dump becomes a reality (which is not always the right answer!) The last thing you need to be doing is flying along in an airplane that will be going straight up for a brief period and then stopping from a slow and dimensioning speed. My suggested set up in the previous email will give you a steady rate of weight off, which can be managed.
I don’t have in a good feeling with banking and keeping the nose lowered while every thing is deteriorating. This how Robert McCurdy explained a way to control the excesssive pitch-up in a recent AAU “In My Humble Opinion” article. Oh yeah, you can over ride the stop with your thumb. It’s real easy.—Seyalin
Bill;
I had to run out to the airstrip, so I put on about 160 gallons of water, set the dump gate around .75 of an inch opening, climbed to 500 feet, levelled off at 150 mph, hand on the grip, then released the water. You get a very rapid climb. With this setting, if an inadvertent dump caught you by surprise you could very easily close the gate or bypass the stop (I asked Pete Jones (Air Repair) does the Thrush have this bypass feature and he said they did not.).
I think this would be, by far, a safer practice than all the other techniques. When you adjust your gate for liquid, simply crank your stop to this safe position!—Seyalin
Lin;
Nothing like a real test to determine a safe procedure. Sorry about the delay in getting back to you, been on the road.
Obviously, wide open for dry and that may not be enough. As for a liquid emergency dump, assuming you get enough upward lift with the .75” opening, safely, then maybe.
But, you did this with power, right? The .75” is may be good practic for takeoffs, when you misjudged runway length and prevailing conditions.
However, if you have the opportunity, try it with a rapid power reduction to ground idle (please, at a safe altitude). I think you’ll note a significant difference in the aircraft’s response. The .75” may not be enough. I’d love to be a house fly on the windscreen inside the cockpit when you try to reduce power and dump all at the same time with your left hand! —Bill
P.S. - Pete should know, but all my Thrush aircraft that I owned (only four, radials and turbine) had a lever by the dump handle that you could use to adjust the gate opening. It was the same lever used to adjust the opening for dry. I don’t see why that wouldn’t work for what you are saying. It could also be bypassed. But with a full load against the stop, I couldn’t bypass the stop. -BL
Bill;
Well, the flight manual for at 502-34 has lots to say about all the different procedures of flight. The manual even describes a fire bomber run, which would really be a way to practice dumping water safely!
The only real concern I had was to have a publication announce that you should practice dumping a load, I think that it should be followed with how to do it correctly and safely!
In the Air Tractor flight manual, it basically says if you hear a loud bang or you start to slow down or if your ITT starts going up — dump your load. I don’t believe that in the middle of an engine failure or when a strange noise or bang goes off you put your hand on the dump handle. I have to admit I have slid my hand over there more than once on departure, but only because the trees were getting taller!
When you pull the power lever all the way back, you are in a way more dangerous position than having a power failure, the prop acts as somewhat of an air brake with a voluntary power reduction. I really would not look forward to a power off dump, if you have ever pulled the prop in to feather at the threshold you know the airplane gains airspeed (it will put you back in your seat). That’s why setting the hopper gate stop around 3/4 to 1 inch opening will give you plenty of a steady weight off plus you can stop it or override it to arrive at your appointed destination!
Hope this isn’t too much yakking about one subject, but just thought I’d share a practice of mine!—Seyalin
Lin;
It’s never too much “yakking”, when it addresses ag-aviation safety. For once, someone, in this case you, refers to the flight manual. The reason for this discussion was to bring out other ideas about how to safely salvo a load. For aerial firefighters, this is executed at a reduced airspeed with flaps. Also, most have computerized gate boxes for precision dumping, instead of a wide open salvo.
Your comment about the pitch of the prop is interesting and true. Although, the prop does go to feather, albeit slowly, when the engine fails, therefore my contention for the ability to execute a full dump. To see how long this takes, you can shut down your turbine engine on the ground without pulling the prop lever to feather. For an emergency, the time it takes for the prop to feather is too long, thus working as an air brake until it does.
You know, there are two basic scenarios going on here. One in a highly conscience state of mind in a takeoff situation and the other going across the field while thinking about the next pass or what have you. As you know, when turbines fail, they are notorious for doing it all at once and sometimes without warning. I think the .75” setting may be appropriate in a takeoff situation, to “milk” the aircraft over the trees, if you are convinced the turbine engine will not catastrophically quit. I have had two turbine engine failures on takeoff, so I’m not convinced.
Once the aircraft is in the air at cruise or across the field, or even in the turn, probably about the only time you are going to be dumping is with an engine failure. Assuming that it is catastrophic and in the worst case scenario, low and slow and the prop goes into feather way too slowly, you’ll need to get rid of the load as expeditiously as possible. In that case, a wide-open dump. You could possibly be faced with a violent up pitch. If that occurs, falling off to the left or right is a good idea.
I think what needs to be done to add credibility to this discussion would be a response from someone who found themselves in such an unfortunate position, catastrophic engine failure, loaded, going across the field...
See ya,—Bill
For any comments about dumping a load, please email: bill@agairupdate.com.
DUNN
AVIATION
BALLIDU AIRPORT
WESTERN AUSTRALIA
ACN: 078 112 580
13th October 2006
FIRST STRIKE FIREFIGHTING + AGRICULTURAL + GENERAL AVIATION
PO Box 17 BALLIDU WA 6606 - Phone (08) 9674 1200 - Fax (08) 9674 1266
Email dunnav@bigpond.com - Website www.dunnav.com.au
Dear Robert
I read with extreme interest your recent article in Ag Air Update. Last year I witnessed a fatal aircraft accident whilst the pilot was doing familiarization flying in one of my AT-602 aircraft. If you follow the link to the Australian website for ATSB (our equivalent to NTSB) you can read the interim accident report.
http://www.atsb.gov.au/publications/investigation_reports/2005/AAIR/aair200505236.aspx
I did not notice much pitch up with the aircraft when the aircraft jettisoned the hopper contents but rather a violent nose down pitching moment about 1 to 2 seconds after the last of the water had drained from the aircraft and I watched the aircraft disappear into the low timber in a near vertical nose down attitude. This particular aircraft produced what I would call on the high end of thrust while in Flight Idle with the Power Lever closed and always required some Beta while landing otherwise it would just keep on floating down the runway.
It became apparent after the Funeral at the pilot’s wake that the a few of the Dromader pilot’s were applying full forward trim to counteract the nose pitch up of the Dromader during firefighting operations, the Dromader being very similar to nose pitch up of the Thrush if you are a bit hot on a drop and very hard to hold the nose down.
I spoke with Leland re the effects of Trim on Airtractor aircraft, Leland responded with it is an FAA Certification requirement to have enough trim to trim back the aircraft to stall speed and enough forward trim to trim through to VNE. I noted with interest that the VNE on the 602 series is 215 mph which is a lot higher than most aircraft. I have spoken to dozens of pilots and they don’t know this trim fact.
It is my belief that the pilot has accidentally gone back to his Dromader ways when the aircraft started to pitch up and applied full forward trim. In bombing I usually get the palm of my hand around behind the stick in anticipation of having to bump the stick forward. In this position it is very easy for the stick to be snatched from your hand if you inadvertently applied full forward trim.
Witness marks that I inspected on the aircraft revealed that at impact the trim was in the full aft position although when the aircraft came to rest 30 feet from impact the trim was in the forward position indicating to me that his hand was on it. I believe that under instinct the pilot went for full back trim after losing grip on the stick to recover the aircraft and then entered a high speed stall situation, which is very easy to do in a Tractor.
My brother and I did the trigonometry on the accident and we believe it was 0.9 of a second from trim application to impact.
As we move into the higher horsepower larger machines I believe that more training is required Globally. Your article in Ag Air Update will be presented to my pilots at the next pilots meeting prior to any commencement of bombing operations. Learning where other people have gone wrong and spreading the word is the hard part. I sometimes just run out of breath trying to convince my crew to back off.
I hope the information that I have passed onto you is helpful and you will spread the word around your traps. The forum of Ag Air Update is great but only a few of my pilots subscribe to it. Maybe a dedicated website like ‘ I nearly killed myself today doing this’ maybe needed to be introduced so Ag pilots all over the world can just log in and have a read and develop a knowledge base of all the traps that lay out their for us Ag Pilots.
Some famous guy wrote once ‘he who does not study history will only just repeat it”
Thank you again for writing the article, I have some 15000 hours of Ag and have never thought to do the roll method in the situations that you described. I don’t fly much anymore as the office has got me but I will spread the word hear in Australia about the roll method.
There are a few horror stories floating around where pilots have nearly bought the farm doing exactly what you described in your article. Thank you once again you will be saving lives!
Kindest Regards
Nev Dunn
Good morning Nev,
My sincerest gratitude to you for your attached letter. I have received several letters regarding the subject of emergency or unplanned dumping of a heavy load. I think this is a subject that has not received a lot of attention, especially from the aircraft manufacturers.
It has been suggested that the dump handle stop (as on Thrushes) be set to allow the dump gate to open only 1/2 of the full open position, thereby preventing the severe pitch-up if the full load is jettisoned. Maybe this suggestion deserves some study. It has also been suggested to me that the "roll maneuver" may be overloading the pilot's attention in the event of an emergency. I do not agree with this.
In our FLYING TIGER AVIATION, Turbine Transition Course, I have added to the take off check list, "Dump handle - unlocked," and in my preflight brief, we discuss the possibility of making an emergency dump on take off, and agree that we will roll to the left or right if we are unable to lower the nose with wings level.
Again Nev, thanks a million for you kind words. It really means a lot to me. Here's hoping we can meet someday.
Best regards,
Robert McCurdy
FLYING TIGER AVIATION, LLC
Chief Pilot / Flight Instructor
On Sep 28, 2006, at 12:24 PM, REEDFLY@aol.com wrote:
Hi Bill,
I just finished reading your e-mail "conversation" with Lin Stanton about dumping. I'm confused about your comments regarding how long it takes the prop to feather. What do you consider to be too long? Thankfully, I've never had a turbine quit on me. But I have purposely shut one down in flight, and then feathered the prop. It took a couple of seconds at the most. I'm sure it takes longer if the prop lever is not pulled back, but that should be part of an emergency procedure continguincy plan.
My personal thought on dumping following a catastrophic engine failure during a spray pass is this. With the dump stop already set at 1 inch, hit the dump handle first, and follow immediately with a yank on the prop lever. The option for a wide open gate dump is still there as I maneuver for a safe landing. All this is done, of course, while simultaneously sucking all the dust and dirt from the cockpit floor directly through my seat.
Rick
From: Bill Lavender <bill@agairupdate.com>
Date: September 30, 2006 1:25:13 PM EDT
To: REEDFLY@aol.com
Subject: Re: Dump
Rick;
You correctly point out an oversight in my conversation with Lin, the option to pull the prop lever back during the emergency. I don't know how much practice it would take to first realize the engine quit (according to studies, two seconds to react), hit the dump lever, the cycle the prop to feather and land. At least you aren't in a twin and trying to figure out which engine it was! (joke).
I'm in agreement, if a pilot can discipline himself to dump, feather and land in a timely fashion, that would seem to be the right thing to do. However, I'm a little in question about your ability to flip the dump lever stop over with 400+ gallons still pushing on the gate, all the while trying to land. My recollection is to reach this lever you'll have your head/eyes out of the line of sight for the landing and probably not have the strength to pull the dump lever back enough (almost closing/shutting) to flip the lever (which hand does that?), and make the landing at the lowest airspeed (empty) possible and as light as possible (inertia).
So, this brings us back to the point of the dialogue, do you dump fully or have the stop lever preventing this?
Great food for thought. You'd think after 75+ years of ag-flight, the procedure would be defined.
See ya,
Bill
On Oct 2, 2006, at 3:12 PM, REEDFLY@aol.com wrote:
Hi Bill,
Good point about the dump lever stop. My 502 has the button on top which allows you to bypass the stop with a minimum amount of effort. My 401, however, does not. And there are a lot of Air Tractors out there which still have that mechanism.
I would say it is virtually impossible to flip the dump lever over with the gate opened part way and 400 gallons pushing on the gate. For one thing, you would need both hands, and that leaves you trying to steer with your knees while everything is going to shit.
I would still recommend the set up I described earlier if the dump lever is equipped with a button release. For those aircraft with the older mechanism, I would leave the lever flipped back to allow a complete dump with one movement. Now that I think about it, that's what I used to do with my older Air Tractors when I sprayed.
I agree that we should have come up with a recommended procedure after all these years. I told Dom, my AT 401 pilot, not to be afraid of using the dump to get out of a bad situation. But I was remiss in not talking in detail about the options.
Rick
From: Bill Lavender <bill@agairupdate.com>
Date: October 2, 2006 3:47:13 PM EDT
To: REEDFLY@aol.com
Cc: Wayne Handley <whandley@inreach.com>
Subject: Re: Dump
Rick;
Right on all points, glad you pointed out the button option. Now, you are in your older AT401, you dump, then what? I don't think it'll be as big of an issue with the radial engine a/c, but the turbine, there is the question of losing control. Of course, there was a loss of a Weatherly during a dumping procedure.
Back to the original discussion topic, what do you do with the aircraft if you elect to do a full dump? However, I've never crossed that bridge in a turbine, but have with a radial, in which I let the material out in a "measured-like" manner. A full dump may be what is needed, but it in itself could be pretty scary, then if you get it under control, you still have to deal with the engine failure!
I wonder if anyone has the initiative to go to altitude and determine what is the best method? I'd think it'd need to be a Wayne Handley effort, with drag and para chutes, just in case things got dicey.
Bill
On Oct 2, 2006, at 2:59 PM, REEDFLY@aol.com wrote:
Bill,
Probably not. But it will feather without oil pressure with the prop lever in either position. When I shut my engine down, I waited a little bit before feathering the prop, and it did immediately. There should have been no oil pressure.
Rick
From: Bill Lavender <bill@agairupdate.com>
Date: October 2, 2006 3:41:10 PM EDT
To: REEDFLY@aol.com
Subject: Re: Prop feather
Agreed.
Bill
On Oct 2, 2006, at 4:07 PM, REEDFLY@aol.com wrote:
Bill,
I don't know that anyone has taken that initiative and I think there may be too many variables to make a definitive recommendation. What kind of airplane is it? How much is in the hopper? Is there a landing area straight ahead? Is it liquid or dry? Do you have flaps already out? It should be noted that not every engine failure is going to require a dump of any kind.
The goal may be to get everbody to simply think through every conceivable situation and have a plan of attack if the emergency occurs. Their subconscience will direct their actions in a nanosecond without having to methodically plod through the various options at that inoportune point in time.
Personally, I am not afraid of losing the aircraft by hitting the full dump. I'm going to peg the stick full forward at the same time and do whatever it takes after that.
Rick
From: Bill Lavender <bill@agairupdate.com>
Date: October 2, 2006 4:12:42 PM EDT
To: REEDFLY@aol.com
Subject: Re: Dump
Rick;
Sounds like a legitimate plan, and probably the one most ag-pilots would follow, instincts. You're probably right about the multitude of variables and who would have the time to figure it all out at that given moment, not me.
See ya,
Bill
What is your opinion/experience? Write aau@agairupdate.com.