[Federal Register: May 8, 1998 (Volume 63, Number 89)]
[Notices]               
[Page 25540-25541]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr08my98-105]

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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]
BILLING CODE 4910-13-M