Edited From the
September Issue of the Central Valley
Aviation News |
Wake Turbulence Avoidance.
A Historical
Examination of the Wake-Turbulence Hazard
1.1 Growing
Concern
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ake turbulence is a natural by-product of
powered flight, but was |
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generally regarded as a serious flight
hazard until the late 1960’s. Upsets
or turbulence encounters associated with
other aircraft were usually accredited to
"propwash" and later on, to
"jet wash". Interest in this
phenomenon greatly increased with the
introduction of large wide-body turbo-jet
aircraft during the late 1960’s, and
a concern about the impact of greater
wake turbulence. This was the impetus to
conduct research to gain additional
information and |
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determine what safety
considerations were necessary as more and
more large aircraft entered the fleets.
1.2 Several Observations Made |
- The strength of
the wake turbulence is governed
by the weight, speed and
wing-span of the generating
aircraft.
- The greatest
strength occurs when the
generating aircraft is heavy, at
slow-speed with a clean-wing
configuration.
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produced (Continued
below left)
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| sufficient information
about the strength, duration and movement
of wake turbulence to come to conclusions
and recommendations on how to avoid it.
The wake was observed to move down
initially and then level off. It was
never encountered at the same flight
level as the generating aircraft or more
than 900 feet below the generating
aircraft. Therefore, a following aircraft
could avoid the wake turbulence by flying
the flightpath of the leading aircraft.
While this can be accomplished in visual
conditions, an alternative was developed
for instrument meteorological conditions.
Aircraft were placed into categories
determined by their gross weight. It |
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was
noted that a decision based on the wing-span of
the following aircraft was a more technically
correct way to establish categories; however, it
did not appear to be an easily workable method.
Since there is a correlation between aircraft
gross weight and wingspan, gross weight was
selected as a means of categorizing aircraft and
wake-turbulence strength. Minimum
radar-controlled wake turbulence separation
distances were established for following
aircraft. The separation distances depend on the
maximum gross certificated take-off weight of
both the leading and following aircraft.
Adjustments in separation distances were made as
more |
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information
on wake-turbulence phenomena was gained during
the 1970s, 1980s, and 1990s, but the basic
concept of using aircraft weights remained
constant. Initially, the
turbojets that were being produced fit cleanly
into distinct categories with logical break
points. For example, heavy air-craft such as the
Boeing B-747, Lockheed L-101 1 and t he Douglas
DC-10 were clearly in a class by themselves.
There were very few regional or business support
size aircraft. Today, there is a continuum of
aircraft sizes as manufacturers developed the
. (Continued below
left)
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| "aircraft
family" concept and produced many
new transport and corporate aircraft.
With improved technology, heavier
aircraft are produced with better
aircraft performance allowing them the
use of shorter runways that previously
could only be used by smaller aircraft.
Additionally, a hub and spoke mix of
regional aircraft with heavyjets, coupled
with an already active private and
recreational aircraft population, results
in a range of wake turbulence strengths
produced and potentially encountered by a
large variety of aircraft |
WAKE-TURBULENCE
SEPARATION CRITERIA
The
wake-turbulence separation |
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criteria, while necessary, are currently
a limiting factor in several airport capacities.
The FAA is working with NASA to develop and
demonstrate integrated systems technology for
addressing separation criteria. The thrust of the
work is to develop wake-turbulence prediction
capability, sensors for detecting wake-turbulence
hazards on final approach and an automated system
to maximize operating efficiency while
maintaining safety standards.
The
effort to gain more information about wake
turbulence continues.
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2 Review of
(some) Accidents and Incidents
National
Transportation Safety Board data show that
between 1983 and 1993, there were at least 51
accidents and incidents in the United States that
resulted from probable encounters with wake
turbulence. In these 51 encounters, 27 occupants
were killed, 8 were seriously injured, and 40
aircraft were substantially damaged or destroyed.
The following are accounts of real events.
1.
A pilot of a medium transport began his take-off
roll about 30 or (Continued below
left)
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40
seconds behind another large transport, and as
the large transport rotated. The large transport
went straight ahead and the pilot of the medium
transport started a left turn at 300 feet with 15
degrees angle of bank. The bank angle violently
increased to 30 degrees from the apparent wake
turbulence of the large transport.
2. A Cessna
Citation 550, on a visual approach, rapidly
rolled left and contacted the ground while in a
near-vertical dive. The two crew members and six
passengers were killed. The Citation was about
2.78 nautical miles (about 74 seconds) behind a
B-757. The flightpath angle of the Citation was 3
degrees and the flightpath angle of the |
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B-757
was 4.7 degrees. Although radar data indicate
that, at any instant, the Citation was at least
600 feet higher than the leading B-757 during the
last 4 miles of the approach, the flightpath of
the Citation was actually at least 300 feet below
that of the B-757.
3. The pilot
of a Cessna 182 was executing an approach to
runway 32. The wind was out of the south at 5
knots. The approach ends of runways 32 and 35 are
about 560 feet apart. The Cessna was at an
altitude of less than 100 feet above ground level
(AGL) when it crossed above the flightpath of the
B-757. The B-757 had passed the crossing position
about 38 seconds prior to the Cessna 182. The
pilot |
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proceeded
"direct to the numbers" of runway 32
and passed above and behind a "Boeing"
that was on final approach to runway 35. The
Cessna experienced a "burble," and then
the nose pitched up and the aircraft suddenly
rolled 90 degrees to the right. The pilot
immediately put in full-left deflection of rudder
and aileron and full-down elevator. As the
aircraft began to respond the aircraft crashed
short of the threshold of runway 32. The pilot
and the two passengers suffered minor injuries,
and the aircraft was destroyed. (Continued below
left)
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Pilot
Responsibilities for Maintaining
| 3-A 5.1 Who
Does What, and When |
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| There is
clear delineation of who and when
responsibility is assumed for avoiding
wake turbulence. The pilot is responsible
for avoiding wake turbulence when: |
| a.
flying in VFR and not being vectored
by ATC |
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b.
maintaining visual separation.
c.
cleared for a visual approach. |
| Air traffic control
(ATC) assumes wake-turbulence
responsibility while providing the pilot
instrument flight rules (IFR) control in
instrument meteorological weather
conditions and when vectoring VFR
aircraft. A discussion of several
situations will help to clarify a pilot's
responsibility. When
the pilot is being radar controlled by
ATC, the aircraft will be spaced, for
wake turbulence, behind a preceding
aircraft at a distance determined by the
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weights
of the two aircraft. Based on the known movements
of wake turbulence, this separation has been
successful in preventing wake-turbulence
encounters. The minimum separation is designed
not only to allow time for the wake turbulence to
begin to dissipate, but also to allow time for it
to descend below the following aircraft's
flightpath. Longitudinal separation is but one
element of avoidance. If VFR weather conditions
exist when ATC is providing radar control, the
pilot is not relieved of the responsibility for
assuring the . (Continued below
left)
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flightpath will avoid
an encounter with wake turbulence. If
instrument meteorological conditions
(IMC) exist, only the ATC established
separation distances are available to
prevent wake-turbulence encounters, since
the pilot is unable to visually apply
avoidance procedures.
To
summarize the points concerning
IFR procedures, the pilot
accepts wake turbulence avoidance
responsibility when:
a. ATC
instructions include traffic
information,
b. instructions
to follow an aircraft
are given and the pilot
is able to comply, and
c. the
pilot accepts the visual approach
clearance. |
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SIC
SAC
Significant
Information for Sacramento
Pilots
From the September Issue of the
Sacramento Aviation Safety Review.
| I |
t would behoove
any pilot, wishing to attend a Pilot
Seminar, to check the listing |
| and confirm times
and dates. Although I almost never
nake(oops) make a mistake sometimes you
will see the day and the date will not
match up. Usually my seminars run on
Wednesday. |
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So if you want to take a
chance, Wednesday will be the best day to come
without checking. However, Seminars have and will
in the future (on an irregular basis) occur on
almost any night. So be prepared. Call the number
listed for contact on the notice.
If you are not
Joe Cool Mountain Pilot and you don’t have
the time or inclination (Heaven Forbid) to get
training or come to one of our Mountain Flying
Seminars, the following List may help you avoid
an unpleasant mountain experience. (Continued below
left)
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- Check the
weather
- Check the
notams
- Review the
performance charts for your aircraft
- Compute
density altitude
- Analyze the
terrain you are going to cross
- Lean the
mixture for best performance
- Fly
indicated airspeeds. In other words you
don’t have to go faster in the
thinner air at higher altitudes.
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8. Cross passes and mountain ridges at a 45 degree angle
9. Plan for up and down drafts.
10. Don’t quit flying the
aircraft
11. Think
12. Think
13. ThinkFrom the September Issue of the
Sacramento Aviation Safety Review.
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Airworthiness
Corner
As promised,
listed below are Seminars available on
request.
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- Detecting and
Reporting Suspected Un-approved
Parts
- Preventive
Maintenance for Pilots and
Technicians
- Certification and
Operation of Amateur Built
Aircraft
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4. Government/Public
Aircraft Operations
5. Completion and Disposition of FAA Form 337’s and Field Approvals
6. Aircraft Maintenance Records and Recording Requirements for Pilots and Technicians |
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7. Facility Inspection of Part 145 Repair Stations (FAA and Air Agency Responsibilities)
8. Aircraft Major Repairs and Alterations
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9. FAA Ticket Program, an Alternative to Legal Enforcement.
10. Remedial Training for Pilots and Technicians, an Alternative to Legal Enforcement.
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Room,
upstairs, Salinas Municipal Airport Terminal
Contact: Jim Chappell
(408) 758-7214
SAN CARLOS AIRPORT
* Flying the Bay Tour
10:00 A.M. Sat.. Sep 5
Location:
Diamond Aviation, 620 Airport Drive, #1.
Contact: Diamond Aviation dispatcher or Karen
Morss
(650) 591-7611
Seating is limited.
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Reservations
are required. SAN
CARLOS AIRPORT
The Flying Companion
7 - 8:30 P.M. Wed Sep 16
Location: West
Valley Flying Club, 701 Skyway Blvd., San Carlos Airport
Contact: West Valley Flying Club dispatcher or George
Kebbe (650) 595-5912
SAN CARLOS AIRPORT
* Cockpit
Resource Management
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10:00 A.M. Sat Oct 3
Location:
Diamond Aviation, 620 Airport Drive, #1.
Contact: Diamond Aviation dispatcher or Karen
Morss (650) 591-7611
Seating is limited.
Reservations are required.
PALO ALTO AIRPORT
Preventive Maintenance
7- 8:30 P.M.Wed Sep 9
Location:
West Valley Flying
(Continued below left)
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Club, 1901 Embarcadero Rd., Suite
100
Contact: West Valley Flying Club
dispatcher or John Pyle (650) 856-2030 PALO ALTO AIRPORT Surviving an
Off Airport Landing
7- 8:30 P.M.Wed Oct 14 Location: West
Valley Flying Club, 1901 Embarcadero Rd., Suite
100
Contact: West Valley Flying Club
dispatcher or John Pyle (650) 856-2030
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REID-HILLVIEW AIRPORT
Flying South of the Border and Beyond
7 - 9:00 P.M. Thu Sep 3
Location:
Nice Air (NE side of apt), 2575 Robert Fowler Way
Contact: Nice Air dispatch
(408) 729-3383 or Mike Shiflet (408) 272-3109
NEW TIME
REID-HILLVIEW
AIRPORT
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Human
Factors in Aviation
6:30 - 8:30 P.M. Thu Sep 10
Location:
Trade Winds Aviation, 2505 Cunningham Ave. (Next
to General Aviation Terminal Building)
Contact: Trade Winds dispatcher or Steve
Gaul at (408) 729-5100SAN JOSE INT’L AIRPORT
Why Smart Pilots do Dumb Things
(Continued below
left
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6:30 P.M. Tue Sep 22
Location:
American Flyers ground training facility, San
Jose Jet Center, 1250 Aviation Avenue, Suite #190
Contact: American Flyers dispatcher,
Darryl Hanamura or Ben Friedman (408) 297-2123SAN JOSE INT’L AIRPORT
Understanding the New FAR Part 61
7 - 9:00 P.M. Thu Sep 24
Location:
General Aviation Terminal Building
(Southeast end of airport)
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Contact: Sherry Diamond (650)
329-2955 or (408) 275-0300 REID-HILLVIEW AIRPORT
Making Better Landings
7 - 9:00 P.M. Thu Oct 1
Location:
Nice Air (NE side of apt), 2575 Robert Fowler Way
Contact: Nice Air dispatch (408) 729-3383
or Mike Shiflet (408) 272-3109
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REID-HILLVIEW
AIRPORT
Wake
Turbulence and Collision Avoidance
7 - 9:00 P.M. Thu Oct 8
Location:
Trade Winds Aviation, 2505 Cunningham Ave. (Next
to General Aviation Terminal Building)
Contact: Trade Winds dispatcher or Steve Gaul
at (408) 729-5100 (Continued below
left)
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* =
Reservations Required
VISALIA (VIS)
Wake
Turbulence Avoidance-
A pilot and Air Traffic Controller
Briefing
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Heighten your
awareness of the factors involved in wake
turbulence.
7 - 9:00 P.M. Thu Sep 3
Location:
Executive Pilots Lounge
Contact: Jim Henry,
(209) 487-5306 x247BAKERSFIELD (BFL)
Wake Turbulence Avoidance- A pilot
and Air Traffic Controller Briefing
Heighten your awareness of
the factors involved in wake turbulence.
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7 - 9:00 P.M. Thu Sep 10
Location:
Mercury Flight Center
Contact: Jim Henry,
(209) 487-5306 x247ATWATER
(MER)
Wake
Turbulence Avoidance-
A pilot and Air Traffic Controller
Briefing
Heighten
your awareness of the factors involved in wake
turbulence.
7 - 9:00 P.M. Thu Sep 17
(Continued below
left)
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Location: Bld 411 Old Castle
AFB
Contact: Jim Henry,
(209) 487-5306 x247FRESNO
(FCH)
Wake
Turbulence Avoidance-
A pilot and Air Traffic Controller
Briefing
Heighten
your awareness of the factors involved in wake
turbulence.
7 - 9:00 P.M. Thu Sep 24
Location:
Chandler Admin.
Building
Contact: Jim Henry
(209) 487-5306 x247
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* =
Reservations Required
As of August 21, 1998, the
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September '98 issue
of the Oakland FSDO edition of the NorCal
Aviation Safety Review had not been received for
publication. This page will be published as soon
as possible upon receipt for publication.
(Continued below
left)
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* =
Reservations Required
MARYSVILLE AREA
(Fly in if you wish)
Mountain Flying
7:00 PM Wed Sep
2
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Location: Yuba County Airport
Ryan Aviation Building
Sponsor: Ryan Aviation
Contact: Larry Ryan
(530)743-8155SACRAMENTO
AREA
(Fly in if you wish)
Are You Fit to
Fly?
Speakers: Dr. Bob
Acthel and a local Flight Surgeon
7:00 PM Thu Sep 3
Location:
Sacramento Executive Airport Airport Terminal
Building
Sponsor: Sacramento Valley Pilots
Association
Contact: Bob Achtel
(916) 452-5391
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CHICO
AREA
( Fly in if you wish)
A Night At The
Movies
Several movies, Including ‘Midair Collision
Avoidance’, "Your Personal Flight’
(a 3 part series) and others.
7:00 PM Wed Sep
16
Location:
Chico Airport Terminal Building Chico, CA.
Sponsor: Pacific Flight Services, Mt.
Shasta 99's
Contact: Diane Schneeweis or Linda Patrick
(916) 893-6727RENO
AREA
(Continued below
left)
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35RD
Annual National Air Races
Top
Airshow Performances, Demonstrations, Static
Displays, The Races (Unlimited, AT-6, Formula
One, and Biplane Classics) and Much More.
BE SURE TO SEE THE FAA’S INFORMATION CENTER
LOCATED IN THE STATIC DISPLAY AREA.
SEP 17 thru 20
Location: Stead AFB, Reno, Nevada
Contact: Reno FSDO
(702) 858-7700NAPA
AREA
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( Fly in if you
wish)
Bird
Strikes and
Language and ATC Problems
7:00PM Wed Sep 23
Speakers:
Birds - Tom Stanton: Language - Lou
Martin, NASA
Location: Napa Airport, IASCO Bldg
Napa, CA
Sponsor: IASCO
Contact: George Cohen
(707)252-3552CLEAR
LAKE AREA
(Fly in if You Wish)
The 19th Annual
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WEST COAST SEAPLANE SPLASH-IN
50th Anniversity of the Lake
Sep 25, 26, and 27
Schedule
of Events
Friday
11:00 AM TO 4:00 PM -
Registration at the Skylark Hotel, Room 130
6:00 PM -Lions Club
Dinner at the Skylark
8:00 PM to ??? Hangar
Flying
Saturday
7 to 10:00 AM -Lions
Club Breakfast at the Skylark (Continued below
left)
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10 AM to 12:00 Noon - FAA
Safety Seminar "Seaplane Safety."
Flying Activities and Presentations all day
11:30 AM to 2:00 PM - Lions
Club Lunch at the Skylark
6:00 PM to 8:00 PM - Lions
Club BBQ Dinner at the Skylark
8:00 PM to 9:00 PM -
Speakers, Sea Wings
Presentations, Recognitions and Raffle Prizes
Sunday
7:00 AM to 10:00 AM - Lions Club
Pancake Breakfast at the Skylark |
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11:30 AM to 2:00 PM - Lions
Club Lunch at the Skylark
Contact: Rob or Karen Davids (209) 736-4554SACRAMENTO AREA
* Operation Takeoff
A three
hour program that covers the services available
from an Automated Flight Service Station. You'll
learn how the system works and how to obtain the
greatest user benefit. A Facility tour is
included.
RESERVATIONS REQUIRED 9:00 AM to 12:00 PM Sat
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Call Ahead For Exact Dates
Location:
Rancho Murieta AFSS, 14670 Cantova Wy,
Ste 101 R. Murieta
Sponsor: Rancho Murieta AFSS
Contact: Mark Oglesby (916) 354-0161 ext. 139SACRAMENTO AREA
* Operation Raincheck
A program
designed to familiarize pilots with the Air
Traffic control system.
(Continued below
left)
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Call for
reservations.
8:00 am till noon
One Sat. per month
Location:
Sacramento TRACON, 5839 22nd Street, Rio
Linda. Off Elkhorn Blvd
Sponsor: FAA Air Traffic Control
Contact: Asst Mgr/Operations (916)
922-9511WINGS
PROFICIENCY AWARD PROGRAM
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FAT FSDO
PHASE
I
V.
Lenny Spivak
PHASE II
Janet
Sloan
Doyle Warkentin
PHASE III
Norman
McAdams
PHASE IV
H. N.
Papadakis
PHASE VII
Gary
Ebel
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PHASE XII
William R.
HaskettSAC
FSDO
PHASE
I
James
E. Bugler
Fred Ides
Gary D. Johnson
PHASE II
Bill
Check
Kenneth Giorgi
PHASE III
Mario
Battierrez
(Continued
below left)
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Michael B. Bee
Chris Cummings
Dale Cummings
Tim HuckabayPHASE IV
Christopher
Temby
Suzanne K. Wooton
PHASE V
Jon Norris
Arthur Payne Jr.
PHASE X
Ted Hedgepeth
Donald O’Connell
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| SJC FSDO
PHASE
I
Axel
Fuchs
Brian A. Heuckroth
William King
Edward C. Shipman
Lisa Sorensen
Eric M. Trehus
PHASE II
Frank
Ashton
Patrick W. Penzias Dirks
Alan Elpel
Brigitte Iwaszkiewicz
Hasher A. Khan
John Wesley Overall, Jr.
Hank Wong
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Susan L. Worster PHASE IV
James
Douglas Frame
PHASE V
Jim Darby
Charles F. de Vogel
Vikas Kapur
Jennifer L. Mellone
PHASE VII
Bill
Woodard
PHASE IX
Anita
Farris
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| NorCal Aviation Safety Review is published monthly by
the F.A.A. Western Pacific Safety Program.
Comments, suggestions and news info are invited. NorCal
Aviation Safety Review reserves the right to
edit all material. Please address all
correspondence to: your local Safety Program
Manager. Edited by Kevin L. Clover - FAA AWP-204 - 5001
Airport Plaza Dr. Ste 100 - Long Beach, CA 90815
- E-Mail kevin.l.clover@faa.dot.gov |
|
