File No. 1-0004
C I V I L
A E R O N A U T I C S
B O A R D
AIRCRAET ACCIDENT REPORT
FRONTIER AIRLINES, INC.
DOUGLAS Dc-3C, N61442
MILES CITY, MONTANA
MARCH 12, 1964
Frontier Airlines Flight 32 of March 12,
1964, crashed and
burnea during an instrument approach to the Miles City Airport,
Miles City, Montana, about 2050 m.s.t.
All five occupants, three
crew members and two passengers were killed, and the aircraft was
destroyed.
Weather conditions last reportkd to the flight were the
operational minima of ceiling 400 feet and visibility one mile.
Wet
snow, strong gusty winds, and near,freezing temperatures prevailed.
Investigation revealea neither malfunc$’ioning of any of the aircraft’s components nor of any of the pertinent airport navigational
facilities including the VOR, which was utilized.
All applicable FAA
certification was in order.
The Board determines that the probable cause of this accident
was the descent below obstructing terrain, for reasons undeterminable,
during an instrument approach in adverse weather conditions.
- 2 -
Investigation
F r o n t i e r A i r l i n e s (FAL) F l i g h t 32 of March 1 2 , 1964, a DC-3C,
N61442, crashed and burned while making an instrument approach t o
t h e Miles C i t y Airport, Miles City, Montana about 2050
-11 March
12,
1964. A l l f i v e occupants, t h r e e crew members and two passengers,
were k i l l e d .
The f l i g h t was r e g u l a r l y scheduled between B i l l i n g s and Sidney
with stops a t Miles C i t y and Glendive, a l l i n Montana,
Departure
from B i l l i n g s was scheduled a t 1950 with a r r i v a l a t Miles C i t y
scheduled a t 2046,
21
The c r e w -
of F l i g h t 32 a r r i v e d a t t h e company's operations
o f f i c e a t B i l l i n g s between 1830 and
1845 t o prepare f o r t h e f l i g h t .
A t about 1925 t h e captain received a weather b r i e f i n g from t h e U. S.
Weather Bureau (USWB) a t t h e airporq.
The c a p t a i n was t o l d t h a t a
cold f r o n t was approaching Miles C i t y a t t h a t time and t h a t gusty
west to northwest winds would p e r s i s t following f r o n t a l passage with
turbulence and a t l e a s t moderate icing.
The captain was a l s o told.
about t h e p o s s i b i l i t y of s q u a l l s i n t h e Miles C i t y a r e a and t h a t t h e
c e i l i n g and v i s i b i l i t y would be somewhat less than i n d i c a t e d on t h e
Miles C i t y 24-hour terminal f o r e c a s t s t a r t i n g a t 1600, March 12.
S p e c i f i c f i g u r e s were not given.
-1/
2/
This f o r e c a s t was i n p a r t as follows:
All times h e r e i n a r e mountain standard based on t h e 24-hour clock,
u n l e s s otherwise noted,
The crew consisted of Captain Kenneth C,, Huber, f i r s t o f f i c e r
Daniel H. Gough, and Stewardess Dorothy Ruth Reif.
- 3 1800 t o 2100, "Pacific frontalcpassage, F e i l1i n g 2,000 f e e t overcast,
v i s i b i l i t y 3 miles, l i g h t know, wind 300 degrees 20 knots with gusts,
occasional v i s i b i l i t y 1mile,' l i g h t snow.
'r
'
FAL's agent a t B i l l i n g s f i l e d a f l i g h t plan. f o r F l i g h t 32 with
t h e Great F a l l s A i r Route T r a f f i c Control Center (WF ArrsCC) about
1920,
It was "Frontier 32, EC-3, f i l e d airspeed 150, proposed o f f
B i l l i n g s a t 0255
2/
requesting 7000 B i l l i n g s V i e t o r 2 t o Miles City."
A Dispatch Release f o r t h e f l i g h t was received from FAL's Denver,
Colorado Dispatch Office about 1920.. A t about
1955 P l i g h t 32
received
i t s Instrument F l i g h t Rules (IFR) clearance from t h e B i l l i n g s Towero
It was read back c o r r e c t l y by t h e f l i g h t as . " A E . c l e a r s F r o n t i e r
A i r l i n e s F l i g h t 32 t o the.Miles C i t y TOR via Victor 2, maintain 7000."
F l i g h t 32 departed B i l l i n g s a t 2001.
l e f t seat, t h e f i r s t o f f i c e r t h e r i g h t .
The captain occupied t h e
T h e , a i r c r a f t * s gross weight
was 23,275 pounds, w e l l under t h e allowable, and i t s c e n t e r of g r a v i t y
was l o c a t e d wfthin prescribed
limits,
A t 2003 t h e f l i g h t reported t o
B i l l i n g s Tower on course and, a t 200bc, leaving 6,000 feet.
A t 2006 B i l l i n g s Tower asked t h e f l i g h t i f it was an estimated
13 miles northeast of B i l l i n g s and t h e f l i g h t r e p l i e d t h a t it was over
Huntley ( a community 10 miles northeast of,BiPPfngs).
A t t h i s time
It d i d soo a t 2007,
t h e f l i g h t was i n s t r u c t e d t o contact W F &C@.
v e r i f y i n g i t s a l t i t u d e of 7,000 f e e t and estimaticg t h e Miles C i t y
VOR a t 2042.
GTF ARTCC acknowledged and asked
t h e f l i g h t i f it was
t
e s t a b l i s h e d on Victor 2.
The f l i g h t r e p l i e d affirmatively,
Greenwich mean time, which i s 1955 m
.
q
q
-4A t 2019, t h e Miles C i t y F l i g h t Service Steation (MLS FSS) c a l l e d
GTF ARTCC and provided t h e 2005 surface weather observation f o r MLS.
T h i s was a s p e c i a l observation and -&e
following data were provided:
Measured c e i l i n g 1,000 f e e t overcast, v i s j b i l i t , y fou:r miles, l i g h t
snow showers, wind 290 degrees, 25 'hmts, peak g m t s 35 hots, a l t i -
meter s e t t i n g 29.42.
The MLS FSS a l s o asked GT!F ARTCG i f FAL 32 was
operating i n accordance w i t h Visual Fl:;,,ght; Rules (WR) or IFR and
was t o l d t h e flight, was 'IFR.
Imraediately, at, 2020, GTF AWN eijnhcted FAL 32 and relayed t o
\
it t h e above s p e c i a l weather report except, flsrr t h e omission of t h e
word
F l i g h t 32 acknowledged.
A t 2030 GTF AmCC asked F l i g h t 32 to "Moni.tor Great Falls f r e -
quency 127.3 nowg'I and t h e f l i g h t acknawkdged,
A t 2032 MLS FSS gave GTF A R E C another s p e c i a l weather report.
This was t h e 2030 observation w h i c h was:
"Indefinite ceiling four
hundred, sky obscured, visibility cineg .moderate sn3W showers
, surface
wind t h r e e zero zero degrees, two zeroo peak @usts t h r e e zeroo a l t i meter two n i n e r four three."
r e l a y t h e above.
GTF
Amc
t k e n i.antacted F l i g h t 32 t o
However, F l i g h t 32 replied "Standby please" because
it was a t t h a t time in contact with t h e FAL agent a% MLS on 129.3 mcs.
receiving t h e MLS weather.
GTF ARTCC d i d contact F l i g h t 32 a t 2033
and gave it t h e above weather report,, again omitting the word "showers".
F l i g h t 32 acknowledged a t 2034,
GTZi' AR'ZX t h e n cleared t h e f l i g h t
-5as follows:
"Roger F r o n t i e r 32 i s c l e a r e d f o r an approach
kl t o t h e
Miles C i t y Airport c r u i s e 7000 contact Miles:City Radio one two s i x
The f l i g h t acknowledged and read t h e
point seven on irritial."
clearance back c o r r e c t l y .
A t 2035, CdllF
AIT'PC@
advised MES FSS "Frontier t h i r t y two Dc t h r e e
estimated Miles C i t y zero t h r e e f o u r two a t p r e s e n t l y c r u i s i n g seven
thousand B i l l i n g s Victor two he has been c l e a r e d f o r an approach your
frequency on i n i t i a l . "
MLS FSS acknowledged and GTF AFQCC then advised
MLS FSS t h a t F l i g h t 32 had.been given t h e 2030 special. weather observation.
A t 2045 f l i g h t 32 reported t o t h e FSS t h a t it was over t h e TOR
s t a r t i n g t h e approach,
weather r e p o r t ,
The FSS acknowledged and gave t h e 2030 s p e c i a l
Also, about 204.5 t h e f l i g h t contacted t h e FBL company
agent a t MLS and advised t h a t it had passe& over t h e VOR a t 2042,- commencing an approach wfth a "fuel o u t of
k-85 g a l l ~ n 2/
~ ~ The
" FAL s t a t i o n
agent read t h e transmission back and gave t h e f l i g h t t h e wind, 290
degrees, 20 wfth peak gusts t o 30 h o t s .
1
The FAL agent %hen advised
6/
t h e f l i g h t t o standby f o r a t r a f f i c check. -
F l i g h t 32 acknowledged.
3
pmcedures
-5/
applicable t o t h e MLS Airport. These are a VQR, ap ADF and two
VOR/DME approaches. Only t h e TOR o r the ADF approaches could have
been u t i l i z e d by F l i g h t 32 as it was not equipped wi%h DME (Distance
(See A t t a c h e n % "At')
Measuring Equipment 1
This means t h a t t h e r e would be
485 gallons of fidel on t h e a i r c r a f t
(without f u e l i n g ) upon departing Miles City.
Since t h e r e i s no c o n t r o l tower at; t h e Miles .City Airport, F r o n t i e r
A i r l i n e s r e q u i r e s t h e i r l o c a l agefit t o make a v i s u a l cheek f o r o t h e r
a i r c r a f t operating a t t h e a i r p o r t and t o r e p o r t t h e r e s u l t s t o i n coming f l i g h t s .
-6The agent checked f o r l o c a l t r a f f i c and advised ''No t r a f f i c sighted
advise i f you want rudder lock on
TUnmya"
2047 and asked f o r t h e rudder lock,
F l i g h t 32 acknowledged a t
The s t a t i o n agent r e p l i e d that
he would have t h e rudder lock ready and asked when t h e f l i g h t would be
on t h e ground.
The f l i g h t r e p l i e d t h a t it would be t h r e e minutes and
t h e s t a t i o n agent acknowledged.
This was t h e f i n a l transmission between
t h e f l i g h t and t h e s t a t i o n agent.
F l i g h t 32 reported a t 2048 t o t h e MLS FSS over t h e VOR inbound.
The FSS r e p l i e d with advisory i n f o m a t i o n t h a t t h e surface wind a t t h e
Miles C i t y Airport was from 300 degrees a t 20 knots with peak gusts
30 knots, favoring Runway 309 a l t i m e t e r 29.43.
and said " w e ' l l p l a n t h r e e zero."
F l i g h t 32 acknowledged
This was t h e l a s t radio contact
between t h e f l i g h t and t h e MLS FSS.
The elapsed time from when t h e a i r c r a f t was over t h e VOR commencing t h e approach (20421, as reported t o t h e FAL s t a t i o n agent, t o
over t h e VOR inbound (20481, as reported t o t h e FSS, ms s i x minutes,
I n none of t h e transmissions from t h e f l i g h t was t h e r e any mention
of operational distress o r of weather conditions encountered.
A t 2050, o r very close thereto, t h e a i r c r a f t s t r u c k t h e ground.
The crash s i t e was appoximately 1-1/2 miles northeast of t h e VOR on
t h e 32-degree r a d i a l of t h e TOR.
I?
The 032 r a d i a l i s on a d i r e c t l i n e from t h e VOR s t a t i o n t o t h e
approach end of Runway 4.
- 7 The crash s i t e was on a 22-degree upslope a t an e l e v a t i o n of
2610 f e e t m.s.1.
and 9,900 f e e t s h o r t of t h e a p p r ~ a c kend of Ruulwsy
4.
The a i r p o r t e l e v a t i o n i s 2,628 f e e t m O s Q 1 0and t h a t of t h e VOR
s t a t i o n i s 2,702 f e e t rnos:l. A:
t k e time of impset t k e aircraft's
heading was about 38 degrees mgr_e-c;f@and t h e e l e v a t i o n of t h e c r e s t
(See A t t a c h e n 3 %">
of t h e small r i s e ahead was 2,615 f e e t m , s o 8 .
A t impact t h e a i r c r a f t was in
8
slfgh5 l e f t wir,g;-d3Tm a t t i t u d e of
about s i x degrees and i n a s l i g h t nose-up a t h i t u d e of &oLt
degrees,
four
The landing gear was extended a r d t h e w5ng f l a p a c t u a t o r was
extended about 8-3/4 inches corresponding to I/& f l a p extension.
After
i n i t i a l impact t h e a i r c r a f t began t o d f s i n t e g r a k and con3inued moving
f o r a distance of about 600 f e e t .
F i r e dev-eloped ar,d t h e major p o r t i o n
of t h e a i r c r a f t was destroyed.
Examination of t h e airframe wreckage, slystems and powerplants
L
,
revealed nothing t o i n d i c a t e t h e r e had been any o p e r a t i o n a l d e f e c t o r
malfunction p r i o r t o impact.
The propeller slash marks i n the ground
were congruent wTtk a groznd speed of 137 h o t s P -
8/
Tke a E r c r a f t was
equipped w t t h de-fcer boots on t h e leading edges ~f the wings am3
empennage and an alcohol a n t i - i c i n g system f o r t h e p x p L l e r s and wPndshield.
It could not be determined if t h e s e fiystems had. been i n use.
F i r e arid o t h e r damage made it h p o s s i b 2 e t o detemim t h e readings
of many instruments.
However, t k e c a p t a i n t s a l t i m e t e r was s e t a t 29*47
The computation assumed a pmbable engine speed of 2050 r.p,m.
-ainches and t h e f i r s t o f f i c e r ' s a t 29.42 inches.
The captainhs Omni
Bearing S e l e c t o r (OBS) was set a t 031; t h e f i r s t o f f i c e r ' s OBS was
not readable,
radio controls.
No frequency information could be obtained from t h e
However, Pnternal e x m i n a t i o n of t h e s e v e r a l u n i t s
showed t h a t t h e No. 1 W communications u n i t was tuned t o company
frequency a t Miles City, t h e No. 2 VHF communication u n i t was s e t on
t h e MLS FSS frequency, t h e No. 1 VHF navigation r e c e i v e r was a t 112.1
mcs,,
( t h e frequency of t h e MLS VOR), and t h e No. 2 TKIF navigation
r e c e i v e r a t 115.3 mcso, ( t h e frequency of t h e Sheridan, Wyoming VOR).
The two ADF r e c e i v e r s were a t 362 kcs. and 247 kcs,
Miles C i t y radio-
beacon frequency i s 320 kcs.
Examination of t h e maintenance records of t h e a i r c r a f t indicated
t h a t maintenance had been current: and as prescribed i n a l l company and
Federal Aviation Agency (FAA) d i r e c t i v e s .
be related t o t h i s accident was disclosed,
No item that could l o g i c a l l y
F i r e a t impact and t h e
t i m e i n t e r v a l before persons reached t h e crash s i t e made it impossible
t o determine i f airframe i c i n g had been present a t impact.
The l a s t o f f i c i a l weather observation taken a t t h e Miles C i t y
Airport p r i o r t o t h e accfdent was t h e 2030 s p e c i a l observation, .the
values of which have been previously mentioned.
Subsequent t o t h e
accident a record s p e c i a l observation was taken a t 2055 and was i n
part:
i n d e f i n i t e c e i l i n g 500 f e e t , sky obscured, v i s i b i l i t y 1 m i l e ,
l i g h t snow showers, temperature 32"F.,
dew-point 32"F.,
wind 300 degrees,
20 knots with gusts t o 30 h o t s , altimeter s e t t i n g 29.44 inches, snow
began a t 2002.
- 9 The Miles C i t y Airport has a' UHF omnidirectional course and
9/
d i s t a n c e information f a c i l i t y (TACAN) .course i n d i c a t o r (VOR)
and a VHF omnidirectional
known j o i n t l y as VORTAC
gether 3-l/2 miles southwest of t h e a i r p o r t .
out of s e r v i c e a t 2015.
111 housed
-9
to-
The TACAN was reported
A technician was dispatched t o t h e f a c i l i t y
and found t h a t t h e TACAN antenna was coated with i c e , which, i n h i s
opinion, was t h e cause of t h e malfunction.
However, t h e TACAN and
t h e TOR a r e separate pieces of equipment and failure of one i n no my
a f f e c t s t h e other.
Since t h e a i r c r a f t was not equipped w9th DME t h i s
f e a t u r e of t h e VORTAC f a c i l i t y could not have been u t i l i z e d .
The FAA
f l i g h t t e s t e d t h e MLS VOR about 0300 t h e f o l l o w k g morning and found
it t o be operating normally.
Statements were taken from 21 persons who saw and/or heard an
a i r p l a n e i n t h e Miles C i t y area near the time of t h e accident.
Inves-
t i g a t i o n revealed no o t h e r a i r c r a f t i n f l i g h t a t t h e approximate place
and time except f o r Northwest A i r l i n e s F l i g h t 40, a EC!-7Cr which
reported over Miles C i t y a t 2035 en r o u t e from B i l l i n g s t o Minneapolis
a t l 7 , O O O feet.
Some o f t h e witnesses were t o t h e sou-bhwest of t h e
MLS Airport (along t h e f l i g h t p a t h from B i l l i n g s ) and some were t o t h e
e a s t and northeast.
-9/
11/
TACAN stands f o r T a c t i c a l A i r Navigation. It f u r c i s h e s both
azimuth guidance and d i s t a n c e i n f o m a t i o n .
VOR stands f o r Very High Frequency Omnidirectional Range.
VOFEAC i s a combining f o m of ITOR and TACAN,
- 10 Three Wtnesses were a b l e t o f i x t h e time of t h e i r observation
q u i t e closely.
One, t h e technician who was sent t o inspect t h e
inoperative TACAN, e s t a b l i s h e d t h a t It was 2048 when he saw an airc r a f t , which he could i d e n t i f y as a E - 3 > pass overhead, toward t h e
a i r p o r t a t a height above t h e ground of approximately 1,000 f e e t and
about 600 feet north of h i s position.
According t o the witness, t h e
a i r c r a f t appeared and sounded normal a t t h i s point,
A t t h a t t h e he
could see t h e glow of t h e r o t a t i n g beacon a t t h e a i r p o r t , 3-l/2 miles
t o t h e northeast.
He a l s o noted weather conditi'ons and estimated
t h a t wind gusts were
35-40 knots "or maybe morettg that t h e wind
was
strong enough t o move s m a l l rocks on t h e ground and that t h e d r i v i n g
snow was very wet.
Another witness, who was i n a parked c a r about
3-l/2 miles south o f t h e a i r p o r t , d i d not see o r hear an a i r p l a n e but
d i d see a red flash i n t h e sky,
lit up ,
"'' a t
VP
,.
t h e whole sky t o t h e west was
a time he e s t a b l i s h e d as c l o s e t o 2050,
gusty wind from t h e north with snow o r s l e e t .
He noted a
A p i l o t d t n e s s was i n
h i s home i n Miles C i t y about one mile southeast of t h e a i r p o r t .
At
about 2050, a time e s t a b l i s h e d by reference t o a t e l e v i s i o n program he
was watching,
I
This
he heard an unusually loud noise from an airplane.
loud noise l a s t e d f o r f i v e t o e i g h t seconds and ended abruptly.
He
described t h e weather as moderate w e t f r e e z i n g snow with wind gusts of
30-40 knots.
Other witnesses were not sure of t h e exact t h e of hearing o r
seeing t h e a i r c r a f t ,
Most of themq however; r e c a l l e d t h e state of
duty a t t h e statim.
The FAA mFr,tsfns an YSS at t h e aSypG-rt, md2 at
The FSS observer . s e d only one rsference pclct,
..
tale
o b s t m c t i o n lights
- 12 i n t h e Manual of Surface (Observations (Weather Bureau, A i r Force,
N a v y ) C i r c u l a r No
The TOR approach procedure p r e s c r i b e s t h a t t h e aircraft starts
a descent f r m
as1
a l t i t u d e not below t h e minimum en route a l t i t u d e
(6,000 f e e t ) t o 4,500
TOR and e::ecutes
f e e t outbound on t h e 211-degree radial of t h e
a procedure t u r n not below t h a t a l t i t u d e .
Upon
completion of t h e procedure t u r n f u r t h e r descent t o 3$500 f e e t i s
authorized while inbound t o t h e s t a t i o n on a 031:degree
course.
A f t e r crossing t h e TOR on f i n a l approach, descent t o 3,900 f e e t i s
authorized u n t i l passing Fort I n t e r s e c t i o n ( a 300-degree bearing from
t h e MLS radio beacon).
authorized.
Further descent t o minimum a l t i t u d e i s then
The night weather minima f o r t h i s approach ( c i r c l i n g )
were c e i l i n g 400 f e e t and v i s i b i l i t y ' o n e m i l e f o r any runway.
L3l
The
procedure as depicted on both t h e U. S. Coast and Geodetic and Jeppesen
approach c h a r t s provides t h a t f i n a l approach i s not authorized from
t h e holding p a t t e r n a t t h e TOR and t h a t a:procednre t u r n must be made.
Following t h i s accident Board i n v e s t i g a t o r s requested FAL t o
i n s t r u c t c e r t a i n F l i g h t 32 crews t o execute VOR instrument approaches
t o t h e MLS Airport f o r t h e purpose of ground witness observations.
The company complied and f l i g h t s were so made on March 15 and
17, 1964.
The f i r s t f l i g h t landed on Rummy 30 and t h e second simulated a landing
on Runway 30 before using Rmway 12.
During both f l i g h t s , i n v e s t i g a t o r s
were present a t c e r t a i n witness locations, w i t h t h e witnesses t o compare
what they s a w and/cr heard w%tht h e i r odsemations on t h e night of
the accident.
a
A c i r c l i n g approach was intended inasmuch as t h e crew advised t h e
FSS of theil- i n t e n t i o n t o use Runway 30.
- 13 The elapsed t h e between t h e reported p o s i t i o n s of t h e s e l a t t e r
f l i g h t s were s u b s t a n t i a l l y t h e same as those reported by F l i g h t 32
of March 12.
During t h e secor,d f l i g h t , engine r.p.m.
and manifold
pressure were .increased t o maximum 1.hits when d i r e c t l y above t h e
c r a s h s i t e i n ar_ attempt; t o d u p l i c a t e t h e sound heard by one witness
immediately p r i o r t o t h e crash of F l i g h t 32 of March 12.
This witness,
an experienced p i l o t , remarked t h a t t h e noise on t h e night of t h e
accident was mmh Louder, seemed t o be lower i n height, and was
followed by complete silznce.
Other witnesses r w a l l e d t h a t what t h e y saw and/or
heard on the
night of t h e accident seened t o be much c l o s e r o r louder t o them than
w 5 a t t h e y saw ar,d/cr heard dmxing t k e s e t e s b .
Analysis
The invest,lgat;l.mxirevealed no k p r c p e r procedures and/or m a l functions of t,& fcdl.L~&ng: dispatch, ground-air communications,
aircraft comp;r-er: t 5: p ~ ~ e - r p l m t sacd
,
pertenent navigational a i r p o r t
aids tc land.frag.
?'_Lcerzfs-e, i t i s i n d l t a k e d t h a t t h e causal f a c t o r s
of this accidor!t a r e r e l a t e d t o either t h e manner i n which t h e air-
craft m s
f l c ~ h x01" %,
t h e p r e v a i l i n g severe weather conditions,
or
t~ a cmblnat;ion t h w e o f .
It 5 s 2mpc:ssLbLe . t o reconskmct t h e p r e c i s e f l i g h t p a t h o r exact
altitades of t h e a i r c r a f t &wing i t s f i n a l few minutes of f l i g h t .
Is E n s t be borne in nind t h a t strcrcg d n d s with blowing w e t snow
and low c e i l i n g s m u l d and probably did s i g n i f i c a n t l y d i s t o r t both
sound and s i g h t i n g s as described by witnesses.
The evidence i n d i -
c a t e s t h a t t h e a i r c r a f t f l e w over t h e VOR a t approximately 2048
about 1,000 f e e t above t h e surface.
The a i r c r a f t a t t h i s position,
according t o t h e witness, appeared and sounded normal i n a l l respects.
Yet, t h e p o i n t of impact was l o c a t e d only L 7 miles from t h e VOR where
t h e minimum descent a l t i t u d e should have been approximately 400 f e e t
above t h e ground.
Because t h e r e i s no evidence of any f a i l u r e o r malfunction of
t h e aircraft o r navigational aids, nor any message received from t h e
crew p e r t a i n i n g t o any d i f f i c u l t i e s , t h e Board cannot state, w i t h any
degree of c e r t a i n t y , t h e reason f o r t h e unexplained departure from t h e
minimum descent altitude.
However, based on t h e evidence a v a i l a b l e
t h e following p o s s i b i l i t i e s appear t o be t h e most p l a u s i b l e :
1. An attempt to Conduct t h e F i n a l Portion of t h e Approach bx
Visual Reference t o t h e Ground
The witness l o c a t e d a t t h e VOR s i t e s t a t e d t h a t v i s u a l
contact with both t h e a i r c r a f t and t h e a i r p o r t beacon was
p o s s i b l e from h i s position.
It is, therefore, possible t h a t
when t h e a i r c r a f t was i n t h e v i c i n i t y of t h e VOR, v i s u a l
contact with t h e ground and/or a i r p o r t beacon was e s t a b l i s h e d
by t h e crew.
If t h i s were t h e case, it i s conceivable t h a t
with both p i l o t s attempting t o maintain v i s u a l contact w5th
the ground and/or keep t h e a i r p o r t beacon i n sight, a con-
tinued wlmonitored descent below t h e e x i s t i n g c e i l i n g s could
have resulted.
- 15 The f i n a l approach speed f o r t h e
E - 3 i s approximately
lo5 knots and t h e a i r c r a f t ' s ground speed a t impact was
computed t o be approximately
137 knots.
Under t h e e x i s t i n g
wind conditions t h e i n d i c a t e d airspeed (IAS) a t impact would
have been approximately
134 knots.
landing gear down and f l a p s
To obtain t h i s speed, w i t h
1/4 extended,
e i t h e r high engine
power s e t t i n g s o r a decrease i n t h e angle of a t t a c k o r a cornb i n a t i o n of t h e two would be required.
The evidence i n d i c a t e s
t h a t normal engine power was being u t i l i z e d by F l i g h t 32 u n t i l
just p r i o r t o impact.
Therefore, it can be postulated t h a t i n order t o cont i n u e t h e f l i g h t by v i s u a l means during t h e f i n a l p o r t i o n of
t h e approach a r a p i d descent became necessary t o remain below
t h e clouds and t o keep t h e ground and/or a i r p o r t beacon i n
sight.
If both p i l o t s were concentrating on conditions out-
side t h e cockpit, and t h e a l t i m e t e r s were m o n i t o r e d , it i s
p o s s i b l e t h a t t h e descent was continued u n t i l contact with
t h e ground was unavoidable.
Power was added by t h e crew when
it was r e a l i z e d they were a t a dangerously low altitude.
However, t h e power a p p l i c a t i o n was too l a t e t o prevent ground
irnpact
2.
Airframe Icin@;
It was determined t h a t weather conditions i n t h e
v i c i n i t y of Miles C i t y were conducive t o moderate t o heavy
- 16 airframe i c i n g i n clouds and p r e c i p i t a t i o n .
Strong gusty
winds over t h e rough t e r r a i n would l i k e l y have produced
moderate t o severe turbulence i n t h e area.
Under t h e s e conditions l a r g e i c e accretions on t h e wing
surfaces, if undetected throughout t h e descent and i n i t i a l
approach, would have become a serious detriment t o airspeed
and a l t i t u d e control, e s p e c i a l l y a f t e r t h e landing gear and
f l a p s were extended.
With such an accumulation of ice, it i s
p o s s i b l e t h a t p r i o r t o o r a t t h e time t h e f l i g h t reached i t s
minimum descent a l t i t u d e (400 f e e t ) , t h e descent could not be
a r r e s t e d withcut a serious l o s s of airspeed.
A s i t u a t i o n of
t h i s type, it i s recognized, could n e c e s s i t a t e lowering t h e
nose of t h e a i r c r a f t t o regain airspeed, r e s u l t i n g i n a rapid
l o s s of a l t i t u d e and operation below a safe t e r r a i n clearance
altitude.
N614b2
was equipped with a de-icing system which
is
normally a b l e t o cope w5th i c e a c c r e t i o n s on c r i t i c a l airframe surfaces.
Because of f i r e and impact damage it was
impossible t o d 5 t e m i n e whether t h i s system was operational
o r i n use p r i o r t o impact.
However, t h e r e were no indications
noted i n any of t h e a i r c r a f t ' s maintenance records p e r t a i n i n g
t o any discrepancies or malfunctions t o t h i s system.
It can,
therefore, be presumed t h a t t h i s system was capable of normal
operation p r i o r t o t h e commencement of t h i s f l i g h t .
Any i c e
- 17 a c c r e t i o n s s u f f i c i e n t t o h a v e c m s e d a l o s s of airspeed o r
a l t i t u d e c o n t r o l should have been known t o t h e crew and,
accordingly, removed from t h e a i r c r a f t through t h e use of
t h e de-icing system.
Additionally,, i c e a c c r e t i o n s s u f f i c i e n t t o cause a
l o s s of c o n t r o l r e s u l t i n g i n ground impact
1.7 miles
beyond
t h e VOR would n e c e s s a r i l y have had t o begin accumulating
considerably f u r t h e r back on t h e approach.
This, i n turn,
would have required t h e use of much higher engine power
s e t t i n g s t o keep t h e a i r c r a f t within t o l e r a b l e airspeeds,
descent rates, and a l t i t u d e s throughout t h e remainder of
t h e approach,
The sound of high engine power heard by t h e
witnesses j u s t p r i o r t o t h e crash i n conjunction with t h e
witness observations of normal engine sounds i n t h e proximity
of t h e VOR suggests t h a t normal power was being employed
u n t i l just p r i o r t o impact.
Further, i f a i r s p e e d and a l t i -
tude c o n t r o l became c r i t i c a l during t h e approach, t h e
landing gear and f l a p s would not normally have been extended
u n t i l a landing on t h e runway was assured.
If they had
a l r e a d y been extended and a s e r i o u s i c i n g s i t u a t i o n developed,
it appears l o g i c a l t h a t one of t h e f i r s t s t e p s taken by t h e
p i l o t would have been t h e immediate r e t r a c t i o n of any drag
producing components.
Finally, t h e a i r s p e e d a t impact, which was determined
t o have been approximately
134 knots,
should have been more
- 18 than s u f f i c i e n t t o counteract t h e e f f e c t s of severe airframe
i c i n g i f such a s i t u a t i o n were present.
The e f f e c t s of severe turbulence combined w i t h heavy
airframe i c e would, of course, c o n s t i t u t e an a d d i t i o n a l
contirol problem.
A s i t u a t i o n of t h i s type would compound
e x i s t i n g c o n t r o l l a b i l i t y problems normally associated with
severe airframe i c e b u t should not have rendered t h e airc r a f t incapable of c o n t r o l l e d f l i g h t .
In conclusion, although e x i s t i n g weather conditions were conducive
t o airframe icing, t h e r e i s i n s u f f i c i e n t evidence a v a i l a b l e t o support
a d e f i n i t i v e f i n d i n g i n t h i s area.
Similarly, t h e evidence will not
support any conclusion that t h e p i l o t committed a gross departure from
proper p i l o t i n g techniques by attempting t o conduct t h e f i n a l p o r t i o n of
t h e approach by v i s u a l reference t o t h e ground.
The Board, therefore,
i s unable t o determine t h e reason f o r t h e a i r c r a f t * s departure below
t h e approved minimun descent a l t i t u d e .
Probable Cause
The Board determines that the probable cause of this accident
was the descent below obstructing terrain, for reasons undeterminable,
during an instrument approach in adverse weather conditions,
BY THE CIVIL AERONAUTICS BOARD:
Is/
ALAN S , BOYD
Chairman
/s/
ROBERT T, MURPHY
Vice Chairman
/s/
Go
/s/
WHITNEY GILLILLAND
Member
JOSEPH MINETTI
Member
I
CHAN GURNEY, Member, did not take p%rL in the adoption of this reportg
Investigation
The C i v i l Aeronautics Board was n o t i f i e d of t h e accident immediately
a f t e r i t s occurrenee.
An i n v e s t i g a t i o n was immediately i n i t i a t e d i n
accordance with t h e provisions of T i t l e V I 1 of t h e Federal Aviation Act
of 1958, as mended.
Depositions i n connection with t h i s i n v e s t i g a t i o n
were taken a t Miles City, Montana, on A p r i l 15, 1964, and a t B i l l i n g s ,
Montana, on A p r i l 16, 1964.
The C a r r i e r
F r o n t i e r Airliries, Inc.,
offSae i n Denver, Colorado.
i s a Nevada corporation with i t s p r i n c i p a l
The corporation holds a c e r t i f i c a t e of
public convenience and n e c e s s i t y issued by t h e C i v i l Aeronautics Board,
and an a i r c a r r i e r operatiRg c e r t i f i c a t e issued by t h e Federal Aviation
Agency.
These c e r t i f i c a t e s authorize t h e c a r r i e r t o engage i n a i r
t r a n s p o r t a t i o n of persons, property, and mail. over t h e rouLe i l i v o l v d .
The A i r c r a f t
The a i r c r a f t was a Douglas model LE-3C,
bore FAA identificat;ion N61442.
s e r i a l number 9642, and
It was manufactured June 1943, and a t
t h e time of t h e accident had been operated 30,442 hours.
had been current arid i n compliance with
Th.e two engines were
watt
Maintenance
FAA requirenents.
and Whitney model R-1830, S l C 3 G and t h e
p r o p e l l e r s were Ha.mil.t,on Standard modcl 23350.
Maintenance of engines
and propell.ers had been current and i n compliance w i t h FAA requirements.
F l i g h t Personnel
Captain Kenneth C. Huber, age 42, had a t o t a l p i l o t i n g time of
15,335 hours of which 12,830 had been i n E - 3 a i r c r a f t .
properly c e r t i f i c a t e d , r a t e d and checked.
He was
H i s rest period, p r i o r t o
t h e start of t h e subject f l i g h t , was i n excess o f 30 hours.
been employed by F r o n t i e r A i r l i n e s , I n c o g s i n c e January
He had
1951, and
was
unusually w e l l experienced, currently, i n landing scheduled F r o n t i e r
A i r l i n e s E-3s a t t h e Miles C i t y Airport.
F i r s t Officer Daniel H. Gough, age 25, had a t o t a l p i l o t i n g time
of 3,539 hours of which 1,355 hours had been a s f i r s t o f f i c e r i n E - 3 s u
He was properly c e r t i f i c a t e d , rated, and checked,
H i s r e s t period,
p r i o r t o t h e start of t h e subject f l i g h t , was i n excess of 30 hours.
He had been employed by F r o n t i e r Airlines, Inc.,
s i n c e June
1962.
Captain Huber and F i r s t Officer Gough had flown together, as a
crew, on numerous F r o n t i e r f l i g h t s i n t o t h e Miles C i t y Airport.
Stewardess Dorothy Ruth R e i f , age 22, had been employed by
F r o n t i e r Airlines, Inc.,
since October 13> 1.963~
MILES CITY AIRPOR
!I 5 1 1 1 P A R l U F N l ,If C O M Y f R C f
YST APCH PRO (FAA)
MILES C I T Y . M O N
C l J A S l ANI1 b l O D E I I C 5 I J I V E Y
I
MILES CITY RADIO
I
b
.
;"'!>I
,4,
5.1 00
/"
I
41
-,
21
LJ f./l
J
6'20'
EMERG SAF;E ALT 100 NM 7400
I
l06"lO'
106°00'
VOR
I
105"50'
105'40'
CAUTION Elevation of Miles
City RBn lower 2800
within 10 miles
authorized minimums within 3 4
miles after passing VOR
2642
Width 01 runways
5600 lost avallabh lor
landlnttr on Rumay 22
-__
FACILITY TO A E R ~ D R O M E : 03 1
3 4 NM
TIME FROM FACILITY TO MISSED APPROACH
4OTS
I 9 0 I 1 0 0 I l l 0 I130 I 1 5 0
t
INlSEC
I
216
-259-VOR-1
10JAN 1964
I
202
I
151
I
134
-
1
121
46'26"
- 105'53'W
031'19Miles
'
,.
,I
. .
MILES CITY. MONT
MILES CITY AIRPORT