[Federal Register Volume 63, Number 89 (Friday, May 8, 1998)]
[Notices]
[Pages 25540-25541]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 98-12293]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
Proposed Change #3 to FAA-P-8110-2, Airship Design Criteria (ADC)
AGENCY: Federal Aviation Administration, DOT.
ACTION: Notice of availability and request for comments.
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SUMMARY: Change 3 is based on a National Transportation Safety Board
(NTSB) recommendation calling for envelope tear warning systems on new
airship certification projects. The recommendation stems from an
airship accident that resulted from an envelope failure. Change 3
requires that some means of indication or warning system will alert the
pilot of envelope tears. This could be an elaborate warning system
based on sensors or simple gauges located and marked such that an
unusual indication would be obvious to the pilot.
DATES: Comments must be received on or before June 8, 1998.
ADDRESSES: Send all comments to: Federal Aviation Administration, Small
Airplane Directorate, Standards Office, ACE-110, 601 East 12th Street,
Kansas City, Missouri 64106.
FOR FURTHER INFORMATION CONTACT: Lowell Foster, Regulations and Policy
Branch, ACE-111, at the address above, telephone number (816) 426-6941.
SUPPLEMENTARY INFORMATION: Any person may obtain a copy of this
information by contacting the person named above under FOR FURTHER
INFORMATION CONTACT.
Comments Invited
We invite interested parties to submit comments on the proposed
change to the ADC. Commenters must identify the report number (FAA-P-
8110-2) and submit comments to the address specified above. The FAA
will consider all communications received on or before the closing date
for comments before issuing the final Change 3 to the ADC. The proposed
changes to the ADC and comments received may be inspected at the
Standards Office (ACE-110), 1201 Walnut, Suite 900, Kansas City,
Missouri, between the hours of 7:30 a.m. and 4 p.m. weekdays, except
Federal holidays.
Background
In 1993, an airship came to rest on top and draped over a seven-
story building in New York, New York, after the airship deflated in
flight and became uncontrollable. The airship suffered a large tear in
the envelope, the material
[[Page 25541]]
that makes up the shape of the balloon portion of the airship. The NTSB
subsequently investigated and recommended several changes to the FAA's
airship design standards. One of the recommendations called for an
envelope tear warning system.
The primary reason for the NTSB's recommendation for the envelope
tear warning system came from the crew's report. The pilot and
passenger both stated that they were not aware of the loss of envelope
pressure until the airship began to collapse, even though there was a
pressure gauge and a low pressure indicator light to alert them of
envelope damage. Although crew procedures for both major and minor
envelope tears had been established, those actions were not
accomplished because the crew did not initially recognize that the
envelope was damaged.
The emergency procedures for this airship, relating to a tear in
the envelope, are to operate the airship with a very low pressure. Very
low pressure causes the airship to lose rigidity, but minimizes the
loss of helium while maintaining controllability. If the emergency
procedure is not followed, ballonets will automatically attempt to keep
the envelope pressure constant, forcing helium out through the tear.
Ballonets are airbags contained within the envelope that are inflated
with air to control the rigidity and sometimes the center of gravity
(trim) of the airship. A warning light and alarm activate when the
envelope pressure drops below a nominal level; however, if the
ballonets continue to automatically inflate to maintain envelope
pressure, the alarm system does not activate until substantial helium
is lost.
The NTSB noted that the airship was not equipped nor required to be
equipped with a ballonet inflation rate transducer or other device,
which might have alerted the crew to the loss of significant quantities
of helium. The NTSB believes that had the airship been equipped with a
better warning system, the pilot would have been alerted to the loss of
pressure earlier and could have taken prudent emergency actions to
improve the possibility of a controlled emergency landing.
Issued in Kansas City, Missouri, on April 30, 1998.
Michael Gallagher,
Manager, Small Airplane Directorate, Aircraft Certification Service.
Proposed Change #3 To FAA-P-8110-2 Airship Design Criteria (ADC)
New Item: Add to 6.2 ``(i)''
Change 3 is based on a National Transportation Safety Board (NTSB)
recommendation calling for envelope tear warning systems on new airship
certification projects. The recommendation stems from an airship
accident that resulted from an envelope failure. Change 3 requires that
some means of indication or warning system will alert the pilot of
envelope tears.
The new paragraph will be added to item 6.2 as follows:
(i) Means to warn the pilot of envelope tears.
Acceptable compliance means include systems as simple as locating
and marking both envelope and ballonet pressure gauges so that unusual
indications (rapid loss of helium) are immediately noticeable to the
pilot. If an airship valving system is complex or automatic, a system
such as a ballonet airflow rate change sensor connected to a warning
system may be more appropriate.
[FR Doc. 98-12293 Filed 5-7-98; 8:45 am]
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