An interesting outgrowth of the Salon article, was the news that a major study was done of the NTSB - at the request of Jim Hall, I believe - by the RAND organization. The results of the study are publically available,and the summary makes for interesting reading.

http://www.rand.org/publications/MR/MR1122.1/MR1122.1.sum.pdf

I would direct your attention to the recommendation on page xlviii in particular.

This would appear to pertain to the question of "involved parties", "interested parties", "designated reviewers" etc.

Should this suggest additional debate, I could post the section of the Aeronautics Act pertaining to that aspect - although I see that interpretations of it have been placed on the site already.

I think the article fails to mention one very important thing. The NTSB simply does not have the money to hire its own experts. Remember that not only is the NTSB in charge of air accident investigation, but also rail, pipeline, marine, and major highway accidents. The article stated :

quote:

---

Experts in a given field, such as engineers, designers and psychologists, are invited to serve on fact-finding committees headed by NTSB investigators. These experts include employees of airlines, aircraft manufacturers and other suppliers.

---

That is true. If they weren't able to do that, they would have no experts at all. The budget just isn't there to hire their own.

From Air Safety Week regarding the Rand Report

Taking exception

Accident
investigations don't necessarily need to get more complicated,
requiring ever more elegant and lengthy levels of detective
work to determine the chain of events leading to
catastrophe. This point was made by C. O. "Chuck" Miller, a
veteran of many accident investigations and now a system
safety consultant. In a recent telephone interview,
Miller took exception to the RAND Corp. assertion that
investigations are growing more challenging as a result of
greater aircraft systems complexity, the "hidden failure
modes" of which are presenting "unprecedented analytical
challenges" (see ASW, Oct. 4).

"Investigations are
getting tough only because admittedly complex information
is buried within aircraft systems," he said. "Hazard
logic trees, sneak circuit analysis techniques, and
designed-in status-at-failure indicators are just some of the
safety engineering approaches available to simplify the
inevitable investigations," Miller explained.

"However, they must be applied. That is not the case very
often now. Of even more importance, if flight data and
cockpit voice recorder (FDR/CVR) information were
captured in real time," Miller argued, "investigators
would have considerably more information at hand than
is often the case today." Even some of the most
modern FDRs are smashed to the point where little
information can be retrieved.

Various concepts for
real-time data capture have been presented in this
publication, and the concept received considerable discussion
at the National Transportation Safety Board's
recorder conference last May (see ASW, May 10). Readers
may recall the comment of Sy Levine, who has proposed
one concept for transmitting data as it's captured.
Levine argued that the current practice of archiving
vital information in shockproof containers is analogous
to monitoring a hospital patient in intensive care,
but paying close attention to the data only after the
patient dies.

Apropos of real-time data capture,
it was announced last week that airline passengers
soon will be able to browse the Internet and to send
and receive e-mails while they travel aloft. The
system, dubbed FlightConnect, is the joint effort of
Tenzing, a U.S. software company, and SITA, the U.S.-based
body which supports aircraft-to-ground communications
for member airlines. The system is an example of the
kind of direct connection that proponents believe
could be applied to flight data recorders. The
capability would eliminate the time delay and potential for
missing data exemplified by the recent search and
retrieval of the flight data and cockpit voice recorders on
the Egyptair Flight 990 accident aircraft.

Regarding the controversial scenario that a relief pilot
may have plunged the Egyptian 767 into its death
dive, the case illustrates the potential utility of
video recording cockpit activity. Video data is seen as
the next great step in the kind of data captured,
according to discussions at the NTSB's recorder conference
earlier this year (see ASW, May 10). A video recording of
events in the cockpit would have shown clearly any
struggle over control of the airplane between Capt. Ahmed
Habashy and relief pilot Gameel Batouti. Such a tape
would aid significantly in countering the skepticism of
the Egyptian government and the widespread perception
in the Arab world of a sinister Western plot to
cover up a mechanical malfunction. >> Miller,
tel. 520/284-9288; Levine, tel. 310/455-1927

More from Air Safety Week regarding the Rand Study:

Review of Accident Investigation Procedures
Eschews Sweeping Reform

RAND Report Finds
Safety Board Spread Thin
"Status quo plus" may best
describe the recommendations resulting from a major review
of accident investigation procedures.

After
more than a year's effort at a cost of some $400,000,
the results of the first independent review of the
National Transportation Safety Board's (NTSB) workload and
the "party system" of accident investigations were
announced last week. The RAND Corporation's Institute for
Civil Justice performed the review at the request of
NTSB Chairman Jim Hall.

The report described
the NTSB as insular, overworked, underfunded,
understaffed, and undertrained for the growing complexity of
accident investigations involving new technology aircraft.
Chairman Hall said simply that he initiated the study
"with no misunderstanding when you ask for a report in
Washington, DC that it comes back saying everything is
rosy."

Regarding the parlous state of fiscal and human resources
for the NTSB's burdensome mission, Hall said bluntly,
"I have repeatedly gone to Congress asking for more
money and personnel, and every year OMB (the Office of
Management and Budget) has zeroed it out."

Hall
hastened to add, "I'm not interested in building a large
bureaucracy."

While recognizing the potential conflict
of interest in the "party system," whereby
manufacturers, airlines, unions, and other organizations
participate in accident investigations, the RAND study
stopped short of recommending any significant change to
the arrangement. For example, one of the issues was
whether or not the parties' role should be expanded from
their involvement in fact-finding to include the
analysis phase of the investigation, and perhaps even
their involvement in the writing of the
report.

Cynthia Lebow, who led the RAND study, said, "We came out
recommending that the party process should stay where it is."
By that she meant the current membership should be
maintained and the parties "should stick to fact-finding,
not analysis."

While endorsing the current
system, Lebow said the limitations of the party system
need to be addressed. For example, the NTSB could
augment its in-house resources by retaining the services
of outside laboratories. The Safety Board, Lebow
urged, needs a "network of sources and expertise so they
can supplement their own knowledge."

Among its
recommendations, the RAND study suggested a whole new mission for
the NTSB: evaluation of aviation security. "This is
an area where we have no expertise," Hall confessed.
In addition, the RAND study recommended that the
NTSB assume a more pro-active stance, investigating
incidents as well as accidents to better identify safety
deficiencies before they result in lost aircraft and lost
lives. Reducing the NTSB's role in investigating general
aviation (GA) accidents might offset the added workload.

Selected Recommendations from the RAND
Review
The NTSB should not...augment the party system by
including family representatives, plaintiff experts,
insurers or other individuals or organizations that have
no direct involvement in identifying the technical
cause of an accident.

The NTSB should move away
from simplistic, one-line probable cause statements
and instead...causal factors should be ranked in
terms of their contribution to the event...

The
NTSB should perform a nationwide assessment of federal
laboratories, universities and independent corporate resources
to identify tools, facilities, and experts capable
of augmenting NTSB resources.

The NTSB
should consider...training state and local investigative
authorities to conduct more routine general aviation accident
investigations.
Source: RAND

Why investigators should be cautious during accident investigations when dealing with industry/manufacturers who might not be all that forthcoming with their information for obvious reasons. Sometimes it's not about outright lying but failing to volunteer information that could be helpful to an investigation but potentially harmful to their organization. If I remember correctly, it was Boeing that was sending their own people out long after the NTSB had ruled out the missile theory, to continue to try to prove that this was still a possibility in what seemed like a desperate attempt to limit their own liability.

This is from an article that appeared in Air Safety Week. The information is from a book called 'Deadly Departures.'

Fuel as a 'Garbage Dump' for Heat

An extract from Deadly Departure: Why the Experts Failed to
Prevent The TWA Flight 800 Disaster and How It Could
Happen Again

By Christine Negroni
(HarperCollins/Cliff Street Books; Publication date February 16, 2000,
256 pages. Note: various on-line booksellers already
are taking orders for the book.)

It could be
argued that Boeing should have made an effort to learn
more about the conditions in the center tank in light
of more than three decades of debate over whether
the isolation of ignition sources was sufficient to
prevent fuel tank explosions.

"It's so difficult
to ignore the fact that you can take off and fly
with a fuel tank bomb," says Charles Anderson, who
worked for Boeing developing fuel tank inerting
technology. In fact, it wasn't difficult to ignore at all.
Until Flight 800, it was a well-kept secret that
industry and the FAA had tallied up the fuel tank
explosions in the past, divided by the number of total
flights, and deemed the hazard an acceptable risk.

"People are suddenly saying to themselves, 'My goodness,
you mean we carry fuel around that can explode?'
Well, we discovered that 40 years ago," said the FAA's
Tom McSweeny, explaining that, "At the time we did
not see a critical safety issue."

In the case
of Flight 800, the significant discovery was how
often the heat sources below the 747 center fuel tank
would send it into the explosive range. The issue then
became how to deal with it.

An important first
question for the board's explosion expert, Merritt Birky,
was whether heat from the air packs was radiant -
that is, did it come off the packs in waves - or
convective - did it move with the air flow.

"You
want to keep the tank cool. If it's convective,
ventilation will help keep it cool. Radiated heat can be
reflected back." Yet Birky felt Boeing was resisting trying
either method of cooling the packs. In the spring of
1998, he realized why.

Birky, Loeb, and other
safety board staffers were meeting with Boeing's (Ivor)
Thomas, 747 chief project engineer Steve Hatch, and fuel
systems engineer Kevin Longwell, kicking around different
suggestions for reducing the temperature in the fuel tank.
Once again a suggestion was made to lay insulation
between the air packs and the tank.

Only this
time, Thomas explained that the heat from the pack bay
was transferred to the tank by design. We use the
tank as a heat sink, he explained.

Loeb
remembers he was "dumbfounded" by the remark. Birky also
felt as if he'd been duped. They were two years into
the investigation, and Boeing had never before told
them that redirecting the heat away from the tank
couldn't be done without damaging the air conditioning
packs. Looks were exchanged among a number of the safety
board staffers attending the meeting, one asking, Are
you saying that you can't insulate because you need
to have the tank absorbing the heat from the pack
bays?

"To us it was an obvious thing to see,"
Thomas said later. "I didn't understand why he was
getting emotional about it. It was like, what's the big
deal?"

Loeb did think it was a big deal, and he
wasn't alone. Among themselves, the safety board
staffers expressed their amazement at the news and their
surprise at the design, Loeb offering his opinion that
"designing an airplane with a fuel tank that is a heat sink
made no sense whatsoever."

This design is not
an uncommon practice though, according to Richard
Hill, the FAA's long-time aircraft fire safety program
manager.

"Normally, there are a number of
airplanes where the heat source is the air conditioning and
the tank above is a heat sink."

Fred Grenich,
a 22-year veteran of fuel systems at Boeing at the
time of the crash, explains why. "Fuel is a BTU
garbage dump. Dump the heat into the fuel and it's not a
problem." The problem arises when there is no fuel in the
tank.

After the disaster, Grenich was assigned to work
on a special in-house investigation into the
circumstances surrounding Flight 800. What he learned changed
his opinion.

"The air conditioning pack under
the fuel tank isn't a great idea," he concluded.
Others on the task force were agreeing with him. Even
Ivor Thomas. "When we looked critically at the air
conditioning packs under the fuel, it became evident it was a
potential problem."

It was a problem specific to
Boeing airplanes. All seven models of Boeing airliners
share the design that places heat generating air packs
beneath a center fuel tank. The McDonnell Douglas
airplanes that became part of Boeing's product line when
the two companies merged in 1997 do not. Airbus
Industries also has air conditioning packs under center fuel
tanks, but a ventilation system successfully minimizes
heating in the tank.

Here is an excerpt from an article entitled: 'Time is running out' (1/20/00) I think it is probably from Air Safety Week. It looks as if even though Boeing had people looking desperately for evidence of a missile having brought down TWA 800 as late in the investigation as '00, they knew right after the 747 crashed that it was probably the fuel tank. Here is an excerpt from the article:

By the way, even though technicians hired by Boeing recently crawled all over the TWA 800
reconstruction searching for potential evidence of a bomb or
missile, other Boeing officials knew early in the tragedy
that the explosion of fuel tank vapors most likely
destroyed the TWA 747, according to a forthcoming book on
the tragedy. Out next month by HarperCollins/Cliff
Street Books, Deadly Departure (subtitle: Why the
Experts Failed to Prevent the TWA Flight 800 Disaster and
How It could Happen Again) by Christine Negroni
offers this vignette:

"By July 1996, Grenich had
left Boeing's military side and was working on the
newest models of 737, Boeing's most popular airliner.
He'd been in his new job just months when he got the
phone call that Flight 800 had crashed and that he was
needed to help look at what might have caused it. His
old friend Ivor Thomas made the call. Before the two
men hung up, Thomas said something Grenich remembers
clearly. 'Dust off all your old data on fuel tank
inerting, Fred. I think we're going to need it.' "

More commentary on Rand report:

http://www.aviationtoday.com/reports/miller.htm

Boeing Could have saved 239+ lives (many of them children)- the technology was there in 1983. TWA 800-Accident? No. I would call it a preventable tragic loss of human life. Why do people accept this? Because it isn't their children/loved ones? Also be sure to see articles below that discuss how Boeing neglected to reveal details of fuel tank problems until 2 yrs. into the NTSB investigation of this tragic crash which shocked the investigators. What is it again that Mr. Bouchard (TSB) said about the industry being so caring and honest and wanting to do the right thing? Yes they are caring alright- mostly about their bottom line.

From this weeks; Air Safety Week
--------------------------------------------------------------------------------
December 23, 2002
Volume 16 Issue 48



--------------------------------------------------------------------------------

Lightweight System Proposed to Increase Fuel Tank Safety

Heavier but more capable system proposed and patented nearly 20 years ago

Aircraft manufacturer Boeing [BA] patented a conceptual system to thwart fuel tank blasts in 1983 that probably would have saved the lives of the 239 passengers and crew killed in three center wing tank explosions since - had it been deployed. The design was discovered in a recent search of the U.S. Patent Office database.

A reduced-weight system for which Boeing recently submitted a request for supplemental type certification [STC] weighs less than the original design and provides lower margins of safety. The STC application applies to B747 classics and all models of the B737, including the Next Generation series.

The discovery of the now-expired patent comes at a time of intense concern about fuel tank safety in Boeing aircraft with heated center wing tanks. The term "heated" refers to the installation of air conditioning packs immediately below the center wing tank [CWT]. Heat generated by the packs during operation rises, transferring into the tanks and causing the fuel to evaporate into a vapor. The vapor-air ullage, or the gas in the space between the surface of the liquid fuel and the walls of the CWT, is explosive about 30 percent of the time. An ignition source in the fuel quantity probes, the fuel pumps, wiring or other components can trigger an explosion of the ullage.

The Boeing patent indicates that the manufacturer was aware of the potential for disaster many years ago and conceived a system for installation in both military and commercial aircraft. It was never developed to the point of deployment in commercial aircraft. Boeing was unable to provide a response by deadline to the "why not?" question, but three possible explanations come to mind: (1) the absence of a regulatory requirement to do so, (2) the system's one-ton weight, and (3) competitor Airbus did not need it. Airbus installed a system of directed ventilation for its CWTs which pumped excess heat overboard, both on the ground and in the air (see ASW, Aug. 10, 1998).

The patent, which expired in April 2000, was in effect during the period in which CWT explosions destroyed a Philippine Airlines B737 on the ground in 1990 and in 1996 Trans World Airlines [TWA] Flight 800, involving a B747 in flight. A Thai Airways International B737 suffered a CWT explosion in March 2001, after the patent had expired. The patent also was in effect during the 1997-1998 period in which a joint Federal Aviation Administration [FAA] and industry task force was looking at various means to inert the fuel tanks. This advisory committee was co-chaired by a Boeing official, as was a second advisory committee convened in 2000 to examine further the potential for inerting to increase fuel tank safety.

These task force efforts were an outgrowth of a call from the National Transportation Safety Board [NTSB] to eliminate flammable vapors in fuel tanks. That recommendation was a direct result of the board's investigation into the TWA Flight 800 disaster.

Both advisory committees concluded that inerting was too expensive, too complicated and too heavy for installation in commercial aircraft. Based on these findings, the industry continued to focus on eliminating all possible ignition sources in fuel tanks. However, the Boeing patent contradicts all of the more recent findings against inerting. The patent application claimed that inerting was technically feasible, various design stratagems could lower the weight of the installed system, the nitrogen-enriched air used to inert the fuel tanks could be used for fire suppression in other areas of the airplane, and lower life-cycle costs would result. For all the reasons asserted since why inerting could not be done, the patent application took the opposite course - arguing why it could be done.

Recent events have shown that the preferred hunt for ignition sources has been futile. Indeed, recent revelations have shown an even greater need for some means of reducing the vulnerability of fuel tanks to explosions. Consider:

Emergency airworthiness directives [ADs] were issued Nov. 23 and 24 concerning the potential for faulty fuel pumps in B737, B757 and B747 to create heat sources in excess of 1,100� F, well above the ignition temperature for fuel. These two ADs followed an Aug. 30 emergency AD, also dealing with the dismaying discovery of a pump-related ignition source in the CWT (see ASW, Sept. 9).
That makes three emergency ADs in a span of less than 90 days. And the cause of the overheating apparently has baffled investigators. According to AD No. 2002-24-51, the "extreme localized overheating" occurred in the priming and vapor pump section of the assembly. "The cause of this overheating is believed to be friction between the pump parts; however, the specific cause of the friction is unknown at this time," the AD confessed.
By the provisions of these ADs, operators must carry a greater weight in minimum fuel - 3,000 to 17,000 lbs. - that is greater than the estimated 2,000-lb. weight of a full-up inerting system.
The FAA recently extended the deadline for its fuel system safety review (SFAR-88) from Dec. 9 to Feb. 7, 2003. This review was intended to cap the hunt for ignition sources with new maintenance and inspection practices. However, the latest spate of ADs suggests to numerous industry sources that SFAR-88 - originally intended to reduce ignition sources by 75 percent - is a dead letter.
The FAA recently amended SFAR-88 to allow for inerting as an "equivalent level of safety" to the elimination of ignition sources (see ASW, Sept. 30).
"Shoe bomber" Richard Reid was seated right above or nearly above the CWT of the American Airlines [AMR] B767 he tried to blow out of the sky Dec. 22, 2001. The blast from the bomb could have ignited flammable vapors in the CWT. This case highlights a potential ignition source from terrorist activity inside the aircraft.
The surface-to-air missile attack Nov. 28 on an Israeli Arkia B757 charter jet shows the threat to wing tanks, not just to the CWT, which has been the point of focus since TWA 800. The SAM-7 heat seeking missiles, had they been successful, would have homed on the heat of the airplane's engines, likely exploding just below the wing and hurling a spray of hot shrapnel into the wing tanks, igniting any flammable ullage therein. This case highlights a potential ignition source from terrorist activity outside the aircraft.
The whole fuel system is under threat. The hunt for ignition sources has proven to be analogous to the "whack-a-mole" arcade game. In this game, the player uses a club to bat down plastic moles that pop up randomly out of holes in the playing board. The latest ADs might be described as whacks at hazardous ignition sources that keep popping up unexpectedly.

The failure of the SFAR-88 effort to deliver on its promise of a 75 percent reduction, the emergency ADs, and terrorist attacks are all assaults on the vulnerability of the fuel system to another explosion. One source alluded to a growing sense of urgency to "do something" and to "do it quick."

On Dec. 12, FAA officials proudly revealed at the agency's Technical Center in Atlantic City, N.J., a membrane-based inerting concept that surmounts previous objections about the weight burden of an on board inerting system. The membranes consist of polymeric fibers that separate the air into a nitrogen-rich stream. Each fiber is about the diameter of a human hair. Boeing's 1983 patent featured similar fibers. With an estimated installed weight in a B747 of 160 pounds, the proclaimed system shaves about 1,800 pounds off earlier estimates of system weight. However, it does so by trimming safety margins and sacrificing capability. Instead of a 9-10 percent oxygen content, the reduced weight system allows for a less demanding 12 percent oxygen level by volume in the tank. As such, it may not protect against ignition sources at altitudes below 10,000 feet. FAA officials believe the 12 percent solution is acceptable based on recent test data. According to minutes of the Oct. 30-31 meeting of the International Aircraft Systems Fire Protection Working Group in Atlantic City, "Two things have caused [previous] values lower than 11-12%: a difference in ignition criteria and safety factors added on to experimental values."

"All reported [oxygen concentration] levels that were lower than 11-12% were due either to a disparity in ignition criteria or excessive safety factors added onto the experimental data," according to the minutes.

With its limited capability to generate nitrogen enriched air [NEA], the propounded system also may not provide inerting protection during the descent phase of flight. Nor does it provide NEA to protect the wing tanks. Because the aircraft has been cold-soaked at altitude and the air conditioning system heat exchangers are not working all that hard, the heated ullage problem during descent for the CWT may be minimal. However, takeoff is not the only vulnerable exposure period to terrorist surface-to-air missile attacks. Indeed, military cargo aircraft are equipped with fuel inerting systems to minimize this threat during both takeoff and landing at tactical airfields.

Perhaps more importantly, the system announced at the Tech Center, and for which Boeing has submitted application to install under the aegis of a supplemental type certificate [STC], may not meet the desired performance criteria outlined in the FAA's advisory circular [AC]. The specifications were outlined in AC No. 25.981-2 issued April 18, 2001. Right off the bat, the 12 percent oxygen concentration in the ullage conflicts with the 9 percent level called for in the AC.

Given the apparent performance shortcomings, will the FAA still issue an STC to Boeing? An FAA official said, "ACs provide guidance only and are not mandatory."

He went on to explain that, "In this particular case, the FAA and JAA [Europe's Joint Aviation Authorities] are developing a Special Condition that will include new requirements for nitrogen inerting systems that may include considerations that are currently not in the rule."

The rule, he added, is the preamble to Section 25.981(c) of the Federal Aviation Regulations, which defines the intent of the regulation: to limit CWT flammability "to that of an unheated wing tank." This being the case, and the present estimate that CWTs contain explosive vapors 30 percent of the time and wing tanks five percent of the time, driving the CWT down to a five percent exposure level would mark a significant improvement in system safety.

It also appears that the performance standards in the AC will be adjusted. According to minutes of the fire systems group meeting, "Preliminary descent modeling [of the lightweight system] illustrates good distribution of inert gas with resulting tank oxygen concentrations of approximately 12%, and short holds at 5k feet will improve the inert gas distribution in-tank and help lower the tank average oxygen concentrations."

"The Advisory Circular that has been out about 6 to 8 months will be updated as a result of the new information available," according to the minutes.

This rather cryptic remark hints at the possibility that performance goals will be selectively adjusted - perhaps downward - to accord with the capability of the lightweight system. Beyond the usual problem-solving partnership between government and industry, there is a whiff of collusion in the air.

Whether such a system will satisfy the NTSB's call for elimination of flammable vapors in fuel tanks is problematic. Fuel tank inerting is among the Board's "Most Wanted" safety improvements. In its latest discussion of this imperative, the Board bluntly said it "has expressed concern about the FAA's apparent premise that minimizing, rather than eliminating, fuel tank flammability is an acceptable goal." (See http://www.ntsb.gov/Recs/mostwanted/explosive_tanks.htm)

One things is clear - former NTSB chairman James Hall is unhappy about the recent discovery of Boeing's 1983 inerting patent. Late in the TWA Flight 800 investigation, NTSB officials were highly dismayed to discover, almost by accident, a Boeing study on CWT heating in the E-4B, a military variant of the B747 (see ASW, Nov. 15, 1999). Boeing's March 14, 1980 "Center Wing Tank Fuel Heating Study" showed that ullage in the tank could reach a temperature of 140� F. According to Dr. Bill Kauffman, an explosives expert at the University of Michigan, "This study "provided a warning for TWA 800."

It may be purely coincidental that Boeing filed its patent application four months after the E-4B tank heating study was completed.

Advised of the patent's existence, Hall said, "This is very troubling, as I don't remember any mention of this by Boeing during the hearings or the four-year [TWA 800] investigation."

"I believe the testimony will record that Boeing swore to me that they had given the Board everything they had on fuel tank inerting," Hall added.

A couple of other points on the system weight issue are pertinent. The lightweight system now being proposed as the most viable solution is not considered "flight critical." As such, only one system - rather than two - may have to be installed. If the system was to be designated "flight critical," two systems might be needed for MMEL [master minimum equipment list] requirements, so that the airplane could be dispatched with one system inoperative and still be able to inert the CWT with the remaining system. According to an FAA response to a query on this matter, "The ARAC has stated publicly that reasonable MMEL relief criteria are needed to make any fleet-wide flammability reduction efforts cost- effective."

Fuel tank explosions directly threaten the safety of flight, yet by not specifying the inerting system as flight critical, aircraft theoretically can be dispatched and fly with flammable vapors in the tank.

If the least-weight and least-cost system is now the leading candidate for installation, it may be useful to point to the installed weight of in-flight entertainment systems [IFE]. There has been no raging debate in the industry about whether the value of these systems in attracting passengers was worth their installed weight. Hold two inerting system weights in mind: 2,000 pounds. for the Boeing concept patented in 1983, and 160 pounds for the lightweight system proposed in 2002.

An IFE system with video screens at every seat collectively weighs between 1,700 and 2,000 pounds on the B767-300, 2,800 pounds on the B777-200, and 3,000 pounds on the B747- 400. In other words, these state-of-the-art systems weigh the same or substantially more than Boeing's earlier inerting concept. They are voracious consumers of electrical power, which was one of the objections raised during debates over the power needs of on-board inerting systems. Moreover, the IFEs involve a whole panoply of electrical and wring systems that impose new maintenance and trouble-shooting burdens, reflecting similar concerns that were raised by industry officials in their task force debates over the viability of inerting systems. None of the power, weight, or reliability concerns were "show stoppers" for IFEs, but they were for inerting systems.

As one industry source quipped acerbically, "What are the respective priorities? To entertain the passengers, or to keep them safe?"

Conflicting Conclusions About Inerting
Fuel Tank Inerting Harmonization Working Group final report summary, Aug. 8, 2001 (extracts)

Our conclusion is that fuel tank inerting will take many years to implement and will have an enormous operational impact, with costs that far exceed the benefits.

With technological breakthroughs, inerting may become more practical at some future date.

Cost/Benefit Over 16-year Period
Benefit Cost Cost/Benefit Ratio
$0.441 billion $20.8 billion - 47:1

Fuel Tank Harmonization Working Group Final Report, July 1988 (extracts)

Fuel tank explosions represent less than one percent of accidents that occur in commercial aviation. The FAA has provided an estimate of the cost of future events to be $2 billion over the next ten years, if no fuel system enhancements were made. The flammability reduction techniques studied by the ARAC [aviation rulemaking advisory committee] working group have an economic impact far greater than this [ASW note: Inerting costs were estimated to be in the range of $33 billion to $37 billion over ten years].

In addition, the FAA is conducting a thorough review of current design and maintenance practices, which will act to improve the safety of fuel tanks by addressing ignition source mitigation [ASW note: This is a reference to SFAR-88, in which inerting was recently declared an acceptable alternate means of compliance - a clear admission that all potential ignition sources cannot be hunted down and eliminated].

Boeing, July 15, 1980 patent application (extracts)

The fuel tank inerting concept is applicable to all types of aircraft, including logistic, combat and commercial, although the latter is subject to natural/accident threats only.

In addition to a significant weight saving, the onboard fuel inerting concept of the present invention has the following additional advantages. It does not require a liquid nitrogen logistic support. It does not require periodic service to replenish liquid nitrogen. It eliminates cryogenic problems. The small size inert gas generator, with associated low bleed air requirement, results in a nominal fuel penalty. Further ... the system can be integrated with the aircraft air conditioning and cooling pack ... Air processing equipment for the inert gas generator can be eliminated with an associated weight, volume and cost reduction.

A quick turn around can be achieved by substitution of prefilled high-pressure bottles. Since the high-pressure nitrogen enriched air can be used as a fire suppressant, the fire protection systems aboard an aircraft can be simplified. [ASW note: it may be useful to note the difference between an inertant and an extinguishant. The latter is designed to smother a fire and starve it of oxygen. An inertant is intended to reduce the oxygen content in an atmosphere in which fire could occur.]

Flow rates are based on the system needs of a large aircraft.

Some caveats on Boeing's 1980 claims

'Lessons Learned' from a Boeing (Douglas Products Div.) October 1997 presentation to the Society of Automotive Engineers and the FAA:

Engine bleed air has contaminants that can adversely affect OBIGGS [on board inert gas generating system] components. Filters should be used.
The OBIGGS computer should be resettable in flight.
It's desirable to inert the tank within 30 minutes.
In-tank and in-line oxygen sensors should be added to ensure fuel tanks are inert and the NEA [nitrogen enriched air] supply is adequate.
A system that doesn't store NEA is feasible but may not keep the fuel tanks inert during ground sit.
A system that doesn't store NEA would be overly large to prevent outside air from entering the fuel tanks during a rapid descent.
A retrofit for existing aircraft may require recertification of the aircraft.