Another plus for a tail wheel aircraft

[HA]

once upon a time my future wife was preflighting her airplane for a lesson. She found that it was low on fuel by looking at the gauges, so I told her to taxi it over to the pumps. She had a heck of a time getting it running and could only get it to the pump by continually feeding it fuel with the primer (resourceful farm girl!). When I got on the ladder to fuel it I found one of the caps laying on the wing, and it had RAINED (a lot) the night before. So I started sumping things, and got a huge amount of water out of it. And we continued to get water out of it for a few more flights, even with much rocking of wings etc. It was a valuable preflight lesson for her, and I've used that example often since then.

turned out that some kids looking for racing gas had siphoned fuel out of her airplane. I thought it was pretty funny that they went to all that trouble to get that high-octane 80-87 from the 172

[sumpthiscom]

The following letter to the NTSB (note the date of the letter/petition) received no response from the NTSB.

Robert E. Scovill JR
E-mail: rescessna@comcast.net
Web Site: http://www.sumpthis.com/
July 31, 2001

Ms. Carol J. Carmody, Vice Chairman and Acting Chairman National Transportation Safety Board
490 L'Enfant Plaza East SW
Washington, DC 20594-0003






Subject:
__________________________________________________

This affidavit is submitted to the National Transportation Safety Board (NTSB) pursuant to Title 49 of the Code of Federal Regulations (CFR) part 845 section 51 (cite: 49CFR845.51): Investigation to remain open. Accident investigations are never officially closed but are kept open for the submission of new and pertinent evidence by any interested person. ...


And pursuant to Title 49 (CFR) part 845 section 41 (cite: 49CFR845.41) petition is hereby made for reconsideration or modification of NTSB's findings and determination of probable cause for aircraft accidents involving general aviation aircraft equipped with Cessna Integral Wing Tanks. Based on new evidence, this petition seeks reconsideration or modification of relevant aircraft accident reports where engine failure or a rough running engine occurred and a probable cause is given as weather (such as carburetor ice), inadequate aircraft preflight or undetermined.
__________________________________________________






References:

Letter R1 to NTSB Chairman Jim Hall dated June 5, 2000 from Robert E. Scovill Jr., Smyrna, Tennessee.

Letter R2 to Robert E. Scovill Jr.; Smyrna, Tennessee dated July 13, 2000 from NTSB Chairman Jim Hall

FAAR3 Safety Recommendations 99.283 and 99.284

Letter R4 L417-02-01-105 to the Federal Aviation Administration (FAA) dated April 11, 2001 from Cessna Aircraft Company





Dear Chairman Carmody:

Previously, I submitted the matter of this affidavit to the NTSB in the letter to former NTSB Chairman Jim Hall mentioned in the above references. That letter was submitted as a safety recommendation for NTSB's consideration. The current letter is a petition submitted to the NTSB for consideration of using new evidence to reconsider the aircraft accidents that are listed further below. To my knowledge, this affidavit is the first formal petition to address topics that have not been submitted for the relevant aircraft accidents as proposed findings in accordance with 49CFR845.27. Thus, in accordance with 49CFR845.41, the subject of this affidavit qualifies as a formal petition to be entertained by the NTSB.


This petition is submitted in the spirit of 49CFR831.4 Nature of investigation, which states that Accident and incident investigations are conducted by the Board to determine the facts, conditions, and circumstances relating to an accident or incident and the probable cause(s) thereof. These results are then used to ascertain measures that would best tend to prevent similar accidents or incidents in the future.





Identification of the new matter:

Attached1: Statement of George Erdel to Robert E. Scovill JR; Smyrna Tennessee dated August 28, 1998.

Attached2: Affidavit as potential witness, Bill Allen, Facilities Manager for MTSU, including his report dated June 2, 1999

Attached3: Affidavit as potential witness, Matt Taylor, Director of Maintenance for MTSU including his report dated October 10, 1999

Attached4: Report by Robert E. Scovill, Jr. dated February 1, 2000.

Attached5: Report number A-83-6, NTSB recommendations to FAA and FAA responses over the years 1983 to 1986.

The first four (1, 2, 3, and 4) attached reports contain results from tests performed on Cessna's integral wing tanks (also called wet wings). The results substantiate that Cessna's integral wing tank design has an indicated design flaw that does not permit positive detection of fuel contamination during a properly performed preflight check. Furthermore, published preflight procedures for some aircraft (later models) equipped with Cessna's integral wing tank include shaking these aircraft's wing and dipping these aircraft's tail to cause fuel contaminants to flow to a wing's sump area for draining. Test results contained in one of the above reports indicate that these procedures appear unlikely to achieve the desired results.


Cessna Aircraft Company's letter to the FAA, L417-02-01-105--obtained through FOIA and listed in the above references--addresses the above topics in the context of FAA Safety Recommendations 99.283 and 99.284. The letter indicates that Cessna Aircraft Company is working with the FAA to investigate Cessna's integral wing tank design. The FAA appears to be investigating the indicated design flaw from an aircraft certification perspective. The NTSB needs to investigate the indicated design flaw from an aircraft accident perspective.

In light of the new evidence contained in the attached test reports, the NTSB aircraft accident reports contained in this petition should be examined, and if appropriate, reconsidered for modification to reflect in NTSB's aircraft accident database that the indicated design flaw and published preflight procedures are probable causes.





Affidavits of Prospective Witnesses

Two prospective witnesses of the new evidence have provided affidavits for this petition. Their affidavits and reports by them that substantiate the new evidence are attached.

Prospective witness: Bill Allen, Facilities Manager for MTSU
Prospective witness: Matt Taylor, Director of Maintenance for MTSU


Other Attachments

Attached6: A Recommended Method for Examining Aircraft Accidents Listed in this Petition: Examination of NTSB's CHI92FA020 Report






Why the new matter was not available prior to the Board's adoption of its findings.






1.
It appears that some NTSB investigations of aircraft accidents involving aircraft equipped with Cessna's integral wing tank may not have explored the possibility that the wing tank design and published preflight procedures for it could have been contributing factors or probable causes. The reason for not investigating the wing tank design and preflight procedures may be due to inadequate NTSB investigation procedures or NTSB investigator's lack of experience with these types of aircraft accidents. This petition includes a table of aircraft accident reports by NTSB number involving aircraft that are not integral wing tank equipped. These reports raise questions about NTSB investigating procedures that appear to be subject to overlooking substantial and obvious clues that if properly examined could lead investigators to the discovery of other factors and other probable causes. The additional aircraft accident reports are included for the purpose of comparing investigating procedures found in aircraft accident reports involving aircraft equipped with Cessna's integral wing tank, which also raise questions about inadequate investigation or inadequate investigation procedures.



2.
Historically, the NTSB has issued safety recommendations to the FAA regarding a lack of positive detection of fuel contamination that involved other fuel tank designs such as Cessna's rubberized bladder-type fuel cells. These safety recommendations are documented in the attached Report number A-83-6 in NTSB recommendations to FAA and FAA responses, which were written over the period May 24, 1983 to March 26, 1986. These safety recommendations are significant because they address the same indicated problem, lack of positive detection of fuel contamination, found in Cessna's integral wing tank and published preflight procedures. It isn't clear why the NTSB has not made use of its experience with these safety recommendations to relate similar subject matter.



3.
Compounding the problem for NTSB's ability to recognize the indicated design flaw in its investigations is that throughout the general aviation industry emphasis is placed upon prevention of fuel contamination while detection of it is seemingly downplayed. Regardless of the measures taken to prevent fuel contamination, one must ultimately have a means to detect if prevention has occurred. Without a means for positive detection, no one can know if fuel contamination has been prevented or not. Preventive measures are important, but for the matter at hand, prevention is not the only issue. The issues are positive detection of fuel contamination and positive detection of prevention. It appears that the NTSB's attention has been focused too much on prevention. Turning attention to the topic of positive detection, the NTSB may find clues that justify reconsidering the aircraft accidents contained in this petition.





Grounds Relied Upon

This petition requests that the NTSB reconsider and modify, as appropriate, aircraft accident reports involving integral wing tank equipped aircraft that have probable causes from weather (such as carburetor ice), inadequate aircraft preflight or undetermined. Grounds for doing so are based upon the evidence presented that positive detection of fuel contamination is not assured. A pilot who performs a sufficient preflight check using published preflight procedures on the relevant aircraft system design can be potentially mislead to believe that fuel contamination does not exist when in fact it does. A need to emphasize positive detection is grounds for the NTSB to promote aviation safety by communicating in aircraft accident reports that positive detection of fuel contamination or positive detection of successful prevention of fuel contamination is necessary.


Additionally, it is mandated under law that the NTSB use the results of its reports to ascertain measures that would best tend to prevent similar accidents or incidents in the future. The reports listed in this petition indicate that whatever it is that the NTSB is doing to ascertain measures ... to prevent similar accidents or incidents is not working because similar accidents continue to occur.


The probable causes of primary interest for reconsideration are weather related causes (such as carburetor ice), inadequate aircraft preflight and undetermined.


For the weather-related probable causes, carburetor ice or conditions conducive to carburetor ice are sometimes stated as the probable cause for a loss of engine power, engine failure, rough-running engine or a hesitating engine. These weather probable causes are at best likely but uncertain. How likely or how uncertain is usually implied by the conduciveness of icing as shown on an icing chart and mentioned in a report's narrative. Given knowledge of the new evidence, it appears that for some of the relevant aircraft accidents that icing due to weather is no more likely than fuel contaminated with water. In reconsidering aircraft accidents with probable causes attributed to weather, the NTSB must consider if an investigator made an attempt to determine if fuel contamination was a factor. It is possible, like ice, that a hazardous quantity of water from contaminated fuel was not visible in an investigation. Additionally, it is possible that an investigator used published procedures to take a fuel sample, which according to the new evidence is an unreliable means for detecting fuel contamination. Consequently, in the interest of aviation safety, relevant aircraft accident reports with weather related probable causes should be reconsidered and modified in light of the new evidence.


For the pilot related probable causes, a NTSB investigator evidently, like most pilots, relies on the proper functioning of aircraft systems and published preflight procedures to measure the sufficiency of a preflight check. In light of the evidence presented, the NTSB needs to review its investigating procedures, methods and techniques for determining the sufficiency of a preflight check performed on relevant aircraft. If an investigation does not include investigating aircraft systems and published procedures that are factors in a pilot's preflight check, then the investigation is insufficient due either to inadequate investigating procedures or an investigators lack of total experience investigating the type of aircraft accident involved. Relevant aircraft accident reports with pilot related probable causes should be reconsidered with a focus of attention upon aircraft systems and the corresponding preflight procedures.


For undetermined probable causes, the Board should review relevant reports to determine if the new evidence is applicable.


NTSB's reconsideration should examine all factors related to fuel contamination including aircraft systems and preflight procedures used to detect it.


Aircraft Accident Reports for Reconsideration

The table on the following page contains fifty-seven NTSB Numbers that are believed to be accidents involving aircraft equipped with Cessna's integral wing tank, but this determination is difficult to make. Therefore, the NTSB should use whatever resources it has to determine which of the following reports involve aircraft that are integral wing tank equipped, and examine them for reconsideration under this petition.






Aircraft Accidents by NTSB Number for Reconsideration





ANC88LA149
DEN00LA091
LAX91LA381

ATL85MA286
DEN84FA012
LAX92LA062

ATL86LA252
DEN86FA092
LAX92LA387

ATL88LA071
DEN87LA141
LAX97LA038

ATL95LA048
DEN87LA210
LAX99LA314

ATL97LA099
DEN99LA174
MIA90LA048

ATL99LA042
FTW86FRG17
MIA92LA133

ATL99LA062
FTW90LA082
MIA94LA014

BFO94LA024
FTW92LA097
MIA97LA083

BFO95FA028
FTW94LA107
MIA97LA118

CHI84LA103
FTW95TA187
MKC85FPG02

CHI84LA147
FTW98LA349
MKC85LA188

CHI85LA066
FTW99LA141
MKC90FA044

CHI86FEV01
IAD96LA123
NYC00LA024

CHI92FA020
LAX83FA122
NYC85FA120

CHI92LA056
LAX88LA063
SEA91LA001

CHI92LA073
LAX88LA289
SEA91LA009

CHI92LA111
LAX89LA323
SEA92LA068

CHI94LA075
LAX91FA081
SEA95LA182








The tables that follow on this page and the next contain 194 NTSB numbers for aircraft accident reports that contain information that raises questions about NTSB's investigating procedures. A review of these reports that focuses on possibly overlooked clues for factors and probable causes during an investigation reveals a substantially strong need for NTSB to evaluate its investigation procedures for general aviation aircraft. The NTSB can use the results of such a review to ascertain measures such as examining the above aircraft accident reports involving integral wing tank equipped aircraft searching for possibly overlooked clues that point to other factors and probable causes for reconsideration. Modifying relevant reports to correctly indicate where dangers exist in aircraft systems, preflight procedures and aircraft accident investigating procedures will be a step that best tends to prevent similar accidents. For the sake of safety, the following 194 NTSB aircraft accident reports are in urgent need of answers to some alarming questions.





Aircraft Accidents by NTSB Number for Review





ANC85LA058
CHI92LA112
LAX93LA072

ANC86FA035
CHI94LA085
LAX94LA277

ANC86LA004
CHI95LA110
LAX96LA071

ANC87LA160
CHI97LA068
LAX97LA080

ANC88LA034
CHI98LA147
LAX99LA159

ANC90FA040
CHI98LA255
MIA87FA217

ANC90LA175
CHI98LA335
MIA88FA187

ANC91IA039
CHI98LA348
MIA89LA084

ANC92LA019
CHI99LA336
MIA95LA165

ANC94LA121
DEN00LA059
MIA96LA137

ANC96LA029
DEN84LA147
MIA97LA230

ANC97LA153
DEN84LA229
MIA98LA093

ANC98LA064
DEN85LA249
MIA98TA011

ANC98LA075
DEN87LA150
MIA99LA171

ANC99LA052
DEN89LA054
MKC84LA013

ANC99LA096
FTW00LA115
NYC00LA203

ANC99LA126
FTW86FRA01
NYC88LA030

ATL88LA100
FTW88LA059
NYC90LA037

ATL88LA216
FTW90LA057
NYC93LA048

ATL89LA050
FTW92LA071
NYC95LA067

ATL93LA095
FTW93LA031
NYC95LA135

ATL94LA175
FTW94LA051
NYC98LA042

ATL99LA099
FTW94LA083
NYC99LA156

BFO85LA069
FTW94LA173
SEA93LA103

BFO95LA069
FTW95LA295
SEA94LA023

CHI84LA008
FTW96LA166
SEA95LA040

CHI84LA168
FTW98LA061
SEA95LA208

CHI86FER07
FTW99LA070
SEA97LA151

CHI87LA078
IAD97LA093
SEA99LA078

CHI90LA163
LAX88LA201


CHI91LA148
LAX92LA125









ANC96LA031
CHI99FA052
LAX99LA267

ANC96LA047
CHI99LA069
MIA00FA201

ANC99LA034
CHI99LA082
MIA00LA076

ATL00FA061
DEN01LA011
MIA00LA099

ATL01FA059
DEN88LA082
MIA00LA100

ATL01LA009
FTW00LA036
MIA00LA127

ATL01LA017
FTW00LA071
MIA00LA162

ATL01LA028
FTW00LA182
MIA00LA238

ATL01LA052
FTW00LA248
MIA95LA161

ATL88LA156
FTW01FA014
MIA96LA188

ATL95LA121
FTW01LA078
MIA96LA194

ATL97LA037
FTW01LA146
MIA97LA033

ATL97LA120
FTW88LA061
MIA97LA064

ATL99LA034
FTW90LA050
MIA97LA224

ATL99LA056
FTW96FA108
MIA98LA030

BFO88FA022
FTW98FA024
MIA98LA249

CHI00LA046
FTW98LA091
MIA99LA135

CHI00LA241
FTW98LA204
MKC88LA081

CHI00LA245
FTW98LA210
MKC90LA046

CHI00LA261
FTW98LA357
NYC00LA070

CHI00LA311
FTW99LA008
NYC00LA223

CHI01FA085
FTW99LA058
NYC00LA262

CHI01LA068
FTW99LA064
NYC01LA149

CHI01LA074
FTW99LA066
NYC88LA077

CHI01LA170
FTW99LA185
NYC88LA118

CHI01LA196
FTW99LA205
NYC90LA044

CHI83LA087
IAD01LA037
NYC90LA055

CHI93LA049
IAD96LA060
NYC96LA088

CHI96LA128
IAD96LA065
NYC96LA096

CHI97LA037
LAX01FA198
NYC97LA049

CHI97LA172
LAX84LA179
NYC98LA037

CHI97LA179
LAX96LA151
NYC98LA078

CHI97LA276
LAX97LA033
SEA98LA022

CHI98LA131
LAX97LA129


CHI98LA226
LAX99LA034









This petition encourages the Safety Board to evaluate the evidence presented and reconsider the issue of positive detection with the same urgency expressed in its safety recommendations to the FAA over the years 1983 to 1986. In the current year, 2001, a response from the NTSB to the public about the possibility that fuel contamination may be a contributing factor where probable cause has been routinely reported as weather or undetermined suggests that the NTSB is not treating matters with the urgency needed.


For example, the following excerpt is taken from the article Drainage Flaws Suspected in Cessna Fuel Tanks (2/21/2001. © Flyer Media, Inc.) by James Wynbrandt.







Scovill [the petitioner] said he also suspects that water contamination plays a larger role in fuel-starvation accidents than investigators realize. He suggests that fuel contamination may actually cause accidents where the NTSB has attributed engine failure to an "unknown cause" and where carburetor ice has been suspected as a contributing factor.


When asked about that possibility, NTSB spokesman Keith Halloway said, "We don't discuss hypotheticals. Unless we're conducting an investigation on a particular issue, we don't like to speculate or give any false leads to anything."





In the letter from former Chairman Jim Hall dated July 13, 2000 written to the petitioner and cited further above under references to this petition, Hall states the following.






The Safety Board appreciates your safety concerns and has contacted the Federal Aviation Administration (FAA) to discuss this issue. The board has verified that the FAA has developed and is implementing a plan to determine if the integral wing fuel tanks of Cessna high-wing, single-engine airplanes comply with applicable certification standards. Board staff will carefully monitor the FAA's progress to ensure that appropriate actions are taken. In addition, all Board personnel tasked with investigating general aviation accidents will be made aware of the possibility that water contamination in the integral wing fuel tanks of Cessna high-wing, single -engine airplanes may not be detectable during preflight inspections.





I hope that the Safety Board's disposition on the safety matters discussed in this petition is not reflected in Halloway's statement that the issues are hypothetical. The attached test results are real. The aircraft accident reports in NTSB's database are real. FAA Safety Recommendations 99.283 and 99.284 are real. Title 49 CFR831.4 and Title 49 49CFR845.41 are real. Furthermore, Halloway's use of the words Unless we're conducting an investigation on a particular issue implies that the issues do not have NTSB's attention, which seems contrary to former Chairman Hall's response to me.


Finally, it is appropriate to expect that spokespersons for the NTSB will possess a higher command of the English language than the general public to whom they speak. In their professional capacity as spokespersons, these people are paid to convey useful information to the public. The Safety Board should consider if Halloway's attempt to inform the public is representative of the professionalism that is normally associated with the NTSB.


Halloway said, "Unless we're conducting an investigation on a particular issue, we don't like to speculate or give any false leads to anything."


I suggest that the NTSB scrutinize the above statement. If NTSB aircraft accident reports relevant to this petition are examined with the same scrutiny, the Safety Board will find that the safety issues presented are real, not hypothetical.


I conclude this petition with a request that the NTSB informs me of how best to correspond with the Board regarding the details of the topics presented. I am prepared to discuss relevant aircraft accident reports one at a time, or as a group, either verbally or in writing. I eagerly await the Board's response.


Sincerely yours,



Robert E. Scovill JR

Petitioner











Attachments

1
Statement of George Erdel to Robert E. Scovill JR; Smyrna Tennessee dated August 28, 1998.

2
Affidavit as potential witness, Bill Allen, Facilities Manager for MTSU, including his report dated June 2, 1999.

3
Affidavit as potential witness, Matt Taylor, Director of Maintenance for MTSU including his report dated October 10, 1999.

4
Report by Robert E. Scovill, Jr. dated February 1, 2000.

5
Report number A-83-6, NTSB recommendations to FAA and FAA responses over the years 1983 to 1986.

6
A Recommended Method for Examining Aircraft Accidents Listed in this Petition: Examination of NTSB's CHI92FA020 Report






Table of Contents for aircraft accident reports included in the petition.

[GAHorn]

While it's unfortunate that various authorities are not inspired to be more pro-active and pursue such evidence of hazard... the fact remains that 1) Cessna will doubtless have proof of their compliance with current-mandated design and certification requirements 2) current requirements do not protect against water added to fuel tanks (Doh) ...and... 3) that the "final" responsibility rests with the pilot to assure that the fuel in not contaminated prior to flight. (There is probably no requirement that aircraft fuel tanks be fool-proof with regard to contamination....or for tanks to automatically divest themselves of water,.... nor is that even a possibility. Instead the onus is placed upon the pilot. After all, if only clean fuel is put into the tanks, and if the aircraft is stored and maintained in accordance with procedures intended to maintain airworthiness, then what could go worng? ) (sp)-(grin)

[n2582d]

This link tells the story of C-150 gas tanks and water.
http://sumpthis.com/cessna150andcessna1 ... 24x768.htm

It is interesting that CAR 3, the regs. that the C-170/172 were certified under, doesn't require there to be a sump in the fuel tank as long as the plane has a sediment bowl downstream.

CAR 3.444 Fuel tank Sump 1.jpg

CAR 3.444 Fuel Tank Sump 2.jpg

As most of you know the C-170 did not even have fuel tank drain valves out of the factory--there were only plugs where we now have drain valves. Imagine how much water could have accumulated in our tanks before tank drain valves were installed. As the same tanks were used in the early 172s as in the 170 I wonder if it would be better to leave the drains off the tanks in the 172. It seems to me a clean fuel sample at the tank drains might give a C-172 pilot a false sense of security. CFIs should teach students to take a sample of the fuel at the gascolator and not just drain it onto the ramp. It was only in 1975 that Cessna installed tank drain valves as standard equipment in all single-engine aircraft. FAR 23.971, adopted in 1993, requires newly certified aircraft to have BOTH a drainable fuel tank sump and a sediment bowl. For a tank the size of the C-170/172 the sump would need to have a capacity of one cup.

QUESTIONS
-I'm curious in that test if the water covering the finger strainer displaced fuel all the way to the sediment bowl. If not, how long can a plane run on the fuel from the finger strainer to the carb inlet? Long enough to taxi and takeoff?
-If water were frozen above our fuel tank sump drain what would we see when sumping those valves? If the top of the valve pushed up the ice, I would think the fuel sample would be clean fuel. This might be a problem if one were to fly into an inversion, going from below freezing temperatures at lower altitudes with above freezing temperatures aloft. Under these conditions ice in the tank could turned back to liquid. As long as the water remained frozen in the tank, and didn't cover the finger strainer, it wouldn't be a problem.
-Is our sediment bowl really the lowest point in the fuel system with the aircraft on the ground? I think fuel and water has to work its way uphill from the bottom rear of the doorpost to the inlet of the sediment bowl. In the three point attitude water would tend to collect at this low point before reaching the sediment bowl. If the water were frozen there it could cause fuel starvation. It seems to me that it would not be that hard to add a tee to the left and right fuel line at the low point there and have another line come laterally to a central sediment bowl between them in the belly. A check valve on either side of the sediment bowl would be necessary to keep the left and right fuel systems seperate upstream of the fuel valve. It may be that there are too many flight control cables running in this area to make that a realistic option. C-Mods has this STC available for a drain valve in the base of the fuel valve on the C-170B: http://www.c-mods.com It simply replaces the plug on the bottom of the fuel valve with a SAF-AIR CAV 110 drain valve--a minor alteration in my opinion.

EXPERIENCES
Normally we hangared the Aztec we flew in Indonesia but on occasion we would have to remain overnight away from base. On one of these overnights I found myself in Darwin. It had poured heavily that night (yeah, "it was a dark and stormy night ...") with the aircraft getting soaked on the ramp. The preflight included draining the sumps--everything was normal. After I arrived in Ambon--a small island around 500 miles north of Darwin--I did a postflight on the Aztec before going home. I was shocked to find both gascolators full of water. Why the engines didn't quit mid-ocean I'll never know.

Back when building flight time in the late '70s a friend of mine had "carburetor problems" in a C-150 he was flying. He managed to keep the engine running using the primer much like your future wife did HA. He happened to be a resourceful farm boy. This reminds me of a system MAF had on their aircraft called EFS for Emergency Fuel System. Here's how the Dec. 12 1981 issue FLIGHT International describes it:

MAF EFS 1.jpg

Nate Saint, an early MAF pilot, came up with this idea after seeing a boy on the hood of bus which was chugging up some dirt road in the Andes. The boy was slowly pouring fuel from a can down the intake to keep the bus going.

My father-in-law is a member of a club that had a C-172 which crashed near Huntington lake in the Sierras. The NTSB decided the engine quit because of carb ice. But after reading this I wonder. The pilot probably would have been at or near full throttle as he was climbing in clear weather to go over higher terrain to the east. It seem unlikely that he would have encountered carb ice under those conditions.

CESSNA'S SOLUTIONS
Harlow you said that, "Cessna Aircraft apparently does not consider this subject to be a serious safety issue." On the contrary, if one looks at the history of Cessna Service Letters and Bulletins it appears that Cessna has been trying to solve this issue of fuel contamination for some time. Here's some of what I've found. SLN 71 on May 10, 1949 replaces cork fuel tank cap gaskets with composite rubber ones. S.L. 170/172-18 on Oct. 30, 1959 calls for the use of Parker Seal Lub for sealing the threads on the fuel tank neck. S.L. 170/172 on Dec. 8, 1959 says to fill the gap between the filler neck and the adapter with Parker Seal Lub.

Sealing Fuel Neck.jpg

As I mentioned above fuel tank quick drains were not required when the C-170 was certified but Cessna has been trying to get owners to install them since at least July 18, 1969 when they came out with SE69-15 and Accessory Kit AK150-82A. Again Cessna called for the installation of tank drain valves on Sept. 10, 1979 when they issued SE79-45 with Accessory Kit AK150-82E. This was later superseded by SEB 92-24 and SK150-60 on Sept. 4, 1992. On Oct. 23, 1970 Cessna came out with SE 70-28. This was similar to SL 170/172-18. It called for sealing the filler neck/adapter joint and the screws in the moat with either silicone seal or Permatex No. 2. The lawsuits must have been flying in the early '80s as Cessna issued two Service Information Letters on fuel contamination--Oct. 29, 1980 SE80-87 and July 30, 1982 SE82-36. Another one that seemed aimed at pacifying the lawyers was issued on Aug. 28, 1987. Here SEB 86-5 Rev. 1 requires that a warning placard about fuel contamination be placed in front of the pilot. I thought the new style cap was just a venting issue but according to SEB 92-27 dated Sept. 4, 1992, "This new cap is designed to assist in preventing water from entering into the fuel tank through the filler ports ... ." Probably more of an issue on the flush caps it replaced on other Cessna models than the original style C-170 cap. This Service Bulletin superseded SE 77-6 and SE 77-6 Rev. 1 which also dealt with vented fuel caps. Finally, on April 19, 1996 Cessna issued a revision to SEB 92-26. This one calls for the addition of a fuel quick drain valve at the outboard end of each tank. The fitting to which the drain screws into is riveted and bonded in position. This Service Bulletin announces the availability of Service Kit 170-11A which applies to the 170A and B, and SK 170-10 which is for the straight 170.

SUGGESTIONS
1. Follow Cessnas Service bulletins and letters listed above--most of them anyway. (I'm not planning on my panel being a bulletin board to pacify some lawyer). Maintaining the seals around the fuel tank inlet area would probably eliminate 90% of the water getting into a tank.
2. Use Stat-O-Seal washers under the screws in the moat. See http://www.cessna170.org/forums/viewtop ... 405#p56405
3.After looking at those pictures of where the water pools below the finger strainer it seems the logical fix would be to place the additional drain called for in SEB 92-26 Rev. 1 below the finger strainer--in tricycle-geared aircraft at least.
4. If the fuel lines at the bottom rear of the C-170 are the low points when the plane is on the ground add tees and a sediment bowl as suggested above. This of course would require a field approval. A similar option (for the B model) would be to add a quick drain valve such as the C-mod one to the bottom of the fuel valve (although I think this point is higher than the low point of the lines that feed into it).
5. Have the source of fuel for the primer one of the tanks instead of the sediment bowl and then have the discharge point either just above the carburetor or in each cylinder intake. The primer could then be used as a poor man's EFS as described above. This too would require a field approval.
6. If the plane is going to be stuck out in the rain and you're not sure about the integrity of the caps and fuel tank adapter area, seal off the cap areas. Tape a Ziploc bag over the area if necessary. No field approval required--it's not a permanent installation!

[sumpthiscom]

Where Did the Water Contamination come from?

I have had several people inquire about the source of the water contamination that I experienced. The history of events in my letter to the FAA dated April 1999 that is available on the documents page provides some details on this topic. Since the history of events requires a lot of reading, here I have consolidated these details into a more general explanation that, hopefully, will explain that it doesn't matter where the water contamination came from.

First, my aircraft's fuel caps and access plates were inspected during the tests that were performed. These items proved to be in excellent condition, and maintenance history indicates that they are not the source of water contamination. I purchased my aircraft new in 1981, and with few exceptions, when parked, it is normally kept in a hangar.

Research indicates that water contamination occurred from small quantities of water accumulating over a period of years from condensation and fueling services.

For years, before every flight, I took fuel samples from my aircraft's sump drains during preflight checks, and not once did I detect water contamination in a fuel sample taken from the integral wing tank sump drains. It was my aircraft's mechanic and a FAA representative on scene at the incident of my emergency landing in a field who, for the first time, drained a sample of fuel from a sump drain that showed evidence of water contamination. Following this event, myself, a FAA representative, and the airport manager investigated the fuel services at the airport where I last refueled. Our investigation revealed that the water contamination (about 10 to 12 ounces) found at the incident was not introduced from the airport's fueling services.

Tracing the source of water contamination and correcting the problem is an obvious safety precaution for prevention once it is known to exist. The chronological order of when someone detects water contamination within a chain of events is all-important. If it is not detected during a preflight check, it may reveal itself in-flight resulting in an engine failure that may lead to a forced emergency landing. Regardless of the source of water contamination, a pilot must be able to detect it during his or her preflight check.

Cessna's integral wing tank drainage system can not be trusted to reveal water contamination during a normal preflight check. Given the design of the integral wing tank, if water contamination is discovered and the system is completely drained using every means possible to insure the water contamination has been removed, then simply refueling the aircraft puts a pilot right back into an unknown situation. Taking a fuel sample soon after refueling may or may not reveal if water contamination is present from the refueling. It's a catch-22. In this circumstance, with knowledge of the problem, a real burden of responsibility is placed on a pilot to make a prudent decision to ground the aircraft. If no water contamination is detected, a pilot may make the decision to risk continuing with the flight, but this decision is not fair to or safe for the public over whom the flight will be made.

Water contamination is not a new problem. It is one with which Cessna has experience. I highlight this issue because Cessna has a history of diverting attention away from the real problem--their certified engineering designs that do not function as certified.

For example, AD 84-10-01 R1 (Bladder fuel cells) became effective in 1988. This AD places significant emphasis on the fuel caps. The significance of the bladder tank design is seemingly irrelevant, but it is the bladder tank design that is the source of the problem, not the fuel caps.

In a more recent example, Cessna in correspondence with me has attempted to divert my attention away from their engineering design problems by focusing attention on the source of water contamination. Cessna has not admitted to me that there is a problem with the design of their integral wing tank drainage system. Basically, Cessna has told me that their design meets certification requirements, and they have attempted to turn my attention away from design issues by over shadowing them with emphasis on sources of and correctional procedures for water contamination. You may read the correspondence to which I'm referring to in a letter that I received from Cessna regarding the problem.

For about sixteen years, I placed a lot of confidence in the FAA certification of my aircraft. I now know that it was dangerous to be as confident as I was. Until I experienced one in-flight rough running engine and three in-flight engine failures, I never asked myself, "Why do I never detect water contamination in a fuel sample during a preflight check"? With blind faith, I assumed that the integral wing tank's drainage system works as certified.

Some of you may want to do your own review of NTSB reports for accidents involving engine failure and water contamination that have probable causes that blame weather or pilots. View the reports with the assumption that pilots perform a proper preflight check on an aircraft that has a flawed fuel drainage system. Then ask yourself, "When the engine quit, did it matter where the water came from"? My answer is no. What matters in this assumption is that a pilot performs a proper preflight check and does not detect water contamination.

Yes, it is important to discover the source of water contamination, but it is more important to detect it once it is present.

Here are three NTSB reports for your review.

NTSB Identification: CHI84LA008

NTSB Identification: CHI85FA054

NTSB Identification: CHI92FA020



Or, search the NTSB database for more reports.


Robert E. Scovill, Jr.