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From NASA's Aviation Safety Reporting System�
Number 190
March 1995
The Low-Down on Altimeter Settings
ASRS recently received three reports from three separate operations, all occurring on the same day and referring to the same situation—low barometric pressure at an Alaska airport. Although these incidents occurred at a single north erly location, they offer a reminder to pilots in other parts of the country that the season is not past for unusually low barometric settings. They are also of interest because of several misconceptions expressed by reporters about ATC/FSS responsibilities in regard to altimeter settings. Here are excerpts:
High to Low, Look Out Below!
A general aviation pilot flying in the Great Lakes region encountered an extreme instance of barometric pressure changes. His story also illustrates why it’s important for pilots to note significant changes in barometric pressure readings during preflight checks of weather along an intended flight route:
■ ATIS [reported altimeter] 28.84. No mention of low altimeter was made. Center cleared us [up] to FL330. Leaving FL180, altimeters were set to 28.92 Captain and 29.92 First Officer (F/O). At FL320 Captain’s altimeter, I called FL320 for 330. The First Officer called 330 noticing the wrong altimeter setting on my side. I immediately leveled off and descended to FL330...while resetting my altimeter to 29.92. In the future, I intend to be much more careful when resetting and cross-checking the altimeters, especially when low altimeter settings are reported. I feel this mistake might have been avoided if the ATIS had mentioned the low altimeter setting.
In recording the ATIS, some controllers may emphasize the al timeter setting by stating, for example, “a low 28.84.” Some Flight Service Station briefers also adhere to this practice. However, this procedure is not mandatory.
■ Southeast bound [on airway] at 17,000 feet indicated
altitude, controller reported my altitude encoder indicated 16,000 feet on the readout. I had departed VFR and picked up my IFR clearance at about 4,000 feet... I had set the barometric pressure as provided by Center when clearance was provided. I was approaching a cold front which was lying north to south over Lake Michigan. The controller asked if I had a backup encoder. I said no, and asked for an altimeter setting. The setting provided was 1 inch lower than the previous provided setting (about 100 nm earlier). I reset my altimeter... After the reset my altimeter now indicated 16,000 feet... The problem was evidently a very steep pressure gradient behind an approaching the [cold] front...
■ Destination weather [reported altimeter] 28.83. Prior to initial
descent, the Second Officer received and put the ATIS informa tion on the landing bug card, except the altimeter was written as 29.83... The Captain started [a] go-around at the same time the Tower reported they had a low altitude alert warning from us... ATC does use the term low/low after low altimeter settings. At what setting it is required, I don’t know, but I feel any time it is below 29.00, it should be used. Again, there is no requirement for controllers to notify pilots of unusually low barometric conditions, although many controllers elect to do so. The phrasing “low/low” is a technique used by some controllers to emphasize a particularly low altimeter set ting, but pilots shouldn’t count on hearing it.
A Toss–and a Catch
Altimeter setting mishaps are more often due to human performance fluctuations than the barometric variety. Here’s what happened to a flight crew that forgot to “wipe the slate clean”:
■ The engineer threw the ATIS up onto the center console (or
perhaps he handed it up to me and I put it there). The altimeter on the ATIS called for 30.17 When we set this in up front and ran the approach check, the sharp engineer remembered that he had copied down 29.67 and brought this to our attention. We had turned the ATIS sheet face up rather than the arrival ATIS which he had copied on the [back]. Weather at our destination was 300 feet, and the difference in altimeter settings between 30.17 and 29.67 was 500 feet. Had this not have been caught by the engineer or later through ATC, the results might have been disastrous. This could be the result of having the company departure/ arrival ATIS on the same sheet...
■ We departed [airport] where the local altimeter setting was 28.84... About 15 minutes after reaching cruise altitude— FL410—the copilot noticed we had set 28.92 rather than 29.92 at FL180. We reset the altimeter...and descended to FL410... In over 30 years of flying, this may have been the tenth time that I’ve had an altimeter setting below 29.00. We are careful in setting the hundredths portion (—.92) of the altimeter, but need to consider the total setting (29.92). It can jump up and bite you occasionally.
This Captain recognizes the bottom line: it is the flight crew’s responsibility to ensure correct setting of the altimeter, and to maintain good cockpit communication to catch any errors.
ASRS Recently Issued Alerts On...
A BA-41 emergency due to improper fairing repair Recurring inflight airframe vibrations on the Airbus 320 HF frequency congestion between Singapore and Taipei BA-31 loss of control attributed to B-757 wake turbulence Concerns about new ATC departure sequencing equipment
A Monthly Safety Bulletin from The Office of the NASA
Aviation Safety Reporting
System,
P.O. Box 189,
Moffett Field, CA
94035-0189
January 1995 Report Intake
Air Carrier Pilots General Aviation Pilots Controllers Cabin/Mechanics/Military/Other 1949 582 56 17
TOTAL
2604
飞行翻译公司 www.aviation.cn 本文链接地址：美国ASRS安全公告CALLBACK cb_190.pdf
From NASA's Aviation Safety Reporting System�
Number 190
March 1995
The Low-Down on Altimeter Settings
ASRS recently received three reports from three separate operations, all occurring on the same day and referring to the same situation—low barometric pressure at an Alaska airport. Although these incidents occurred at a single north erly location, they offer a reminder to pilots in other parts of the country that the season is not past for unusually low barometric settings. They are also of interest because of several misconceptions expressed by reporters about ATC/FSS responsibilities in regard to altimeter settings. Here are excerpts:
High to Low, Look Out Below!
A general aviation pilot flying in the Great Lakes region encountered an extreme instance of barometric pressure changes. His story also illustrates why it’s important for pilots to note significant changes in barometric pressure readings during preflight checks of weather along an intended flight route:
■ ATIS [reported altimeter] 28.84. No mention of low altimeter was made. Center cleared us [up] to FL330. Leaving FL180, altimeters were set to 28.92 Captain and 29.92 First Officer (F/O). At FL320 Captain’s altimeter, I called FL320 for 330. The First Officer called 330 noticing the wrong altimeter setting on my side. I immediately leveled off and descended to FL330...while resetting my altimeter to 29.92. In the future, I intend to be much more careful when resetting and cross-checking the altimeters, especially when low altimeter settings are reported. I feel this mistake might have been avoided if the ATIS had mentioned the low altimeter setting.
In recording the ATIS, some controllers may emphasize the al timeter setting by stating, for example, “a low 28.84.” Some Flight Service Station briefers also adhere to this practice. However, this procedure is not mandatory.
■ Southeast bound [on airway] at 17,000 feet indicated
altitude, controller reported my altitude encoder indicated 16,000 feet on the readout. I had departed VFR and picked up my IFR clearance at about 4,000 feet... I had set the barometric pressure as provided by Center when clearance was provided. I was approaching a cold front which was lying north to south over Lake Michigan. The controller asked if I had a backup encoder. I said no, and asked for an altimeter setting. The setting provided was 1 inch lower than the previous provided setting (about 100 nm earlier). I reset my altimeter... After the reset my altimeter now indicated 16,000 feet... The problem was evidently a very steep pressure gradient behind an approaching the [cold] front...
■ Destination weather [reported altimeter] 28.83. Prior to initial
descent, the Second Officer received and put the ATIS informa tion on the landing bug card, except the altimeter was written as 29.83... The Captain started [a] go-around at the same time the Tower reported they had a low altitude alert warning from us... ATC does use the term low/low after low altimeter settings. At what setting it is required, I don’t know, but I feel any time it is below 29.00, it should be used. Again, there is no requirement for controllers to notify pilots of unusually low barometric conditions, although many controllers elect to do so. The phrasing “low/low” is a technique used by some controllers to emphasize a particularly low altimeter set ting, but pilots shouldn’t count on hearing it.
A Toss–and a Catch
Altimeter setting mishaps are more often due to human performance fluctuations than the barometric variety. Here’s what happened to a flight crew that forgot to “wipe the slate clean”:
■ The engineer threw the ATIS up onto the center console (or
perhaps he handed it up to me and I put it there). The altimeter on the ATIS called for 30.17 When we set this in up front and ran the approach check, the sharp engineer remembered that he had copied down 29.67 and brought this to our attention. We had turned the ATIS sheet face up rather than the arrival ATIS which he had copied on the [back]. Weather at our destination was 300 feet, and the difference in altimeter settings between 30.17 and 29.67 was 500 feet. Had this not have been caught by the engineer or later through ATC, the results might have been disastrous. This could be the result of having the company departure/ arrival ATIS on the same sheet...
■ We departed [airport] where the local altimeter setting was 28.84... About 15 minutes after reaching cruise altitude— FL410—the copilot noticed we had set 28.92 rather than 29.92 at FL180. We reset the altimeter...and descended to FL410... In over 30 years of flying, this may have been the tenth time that I’ve had an altimeter setting below 29.00. We are careful in setting the hundredths portion (—.92) of the altimeter, but need to consider the total setting (29.92). It can jump up and bite you occasionally.
This Captain recognizes the bottom line: it is the flight crew’s responsibility to ensure correct setting of the altimeter, and to maintain good cockpit communication to catch any errors.
ASRS Recently Issued Alerts On...
A BA-41 emergency due to improper fairing repair Recurring inflight airframe vibrations on the Airbus 320 HF frequency congestion between Singapore and Taipei BA-31 loss of control attributed to B-757 wake turbulence Concerns about new ATC departure sequencing equipment
A Monthly Safety Bulletin from The Office of the NASA
Aviation Safety Reporting
System,
P.O. Box 189,
Moffett Field, CA
94035-0189
January 1995 Report Intake
Air Carrier Pilots General Aviation Pilots Controllers Cabin/Mechanics/Military/Other 1949 582 56 17
TOTAL
2604
飞行翻译公司 www.aviation.cn 本文链接地址：美国ASRS安全公告CALLBACK cb_190.pdf
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