iELE.ASE DATE_

JUL 2 X 1947 RM No. L7F20

PEA " ^.^: ILE 6py

MICA

RESEARCH MEMORANDUM

A TIME HISTORY OF CONTROL OPERATION OF A C-54 AIRPLANE

IN BLIND LANDING APPROACHES

By

Donald B. Talmage

Langley Memorial Aeronautical LaboratoryLangley Field, Va.

NATIONAL ADVISORY COMMITTEEFOR AERONAUTICI:ILE OOPY

WASHINGTON , To be returned toJuly 18, 1947 the files of the ki-;)Ial

Advisory Commiiwe

or Aefonautics. Washin

https://ntrs.nasa.gov/search.jsp?R=20050019332 2019-08-11T23:42:18+00:00Z

T20

PIONAL ADVISORY COI- IMITTEE FOP, PZRONAUTICS

RESEARCH ILIiORANllUM

A TIME HISTORY OIL' CGYPROL OPE71 OFATION A c--14 IM

AIRPLANE

IPT BT 11,T-) LUDII\TG AT'PROACHES

By Donald B. TaLw%Se

STZIMARY

Tests were made with a. C- j? airplane in whf.ch airline pilotsmade several blind approaches to determine whether an^T special flyin-techniques were used in blina landings and whether any specialhandlinE,-qualities requirements would have to be formulated becauseof such s pecial techniques.

It was founa that the airnla.ne was flown at all times in thenormal iaeay.-ierj that is, all turns were banl:ec? turns that were nearlycoordinated by use of the rudder so that tho sideslip was held closeto zero. The -,)ilot .ex--)ended considerable physical work in continuallynovi.niS^ the controls but this wa'-e eras due in part to the large frictionin the three control systems. The actual control de g°loctions usedwere small to the maximum deflections available.

I.Tvt'MODUCTICN

In October of 1946, f li cht tests were be&;un on a C-54 airplanewhich had been instrviiented con-pletely with standard NACA recordinginstruz-vents to i:ieasure its handlin(s qualities. DurinC the course ofthese tests, three regZ,lar airline pilots made several blind approaches.An Army operated GCA (E,ro!uid.-controlled approach) blind-land.inr,•systei;i eras used. The object in ma-1 -ink these blind approaches was todetermine whether any s pecial flying techniques were used under suchconditions and whether any new handling-qualities re quirements wouldhave to be scat u» because of these special techniques.

RESULTS

A time histor of one of the approaches i s given in ibvre 1.The curves of figure 1 are tracinSs of the continuous -photographicrecords from the standard MACA recording instrunients except for the

2 NACA IN No . L7120

curves showing heading, distance from the center line of the runway,and the antle of bank. These three curves were obtained from motionpictures of the horizon and runway taken by a camera that was mountedrigidly in the nose of the airplane and which was synchronized with theother instruments. The three quantities in question were obtainedeasily fro_,i the geometry of tine system. Because of a faulty instrument.switch, there was an inadvertent break of un]::no,m duration in therecord; howevor, this Brea'_: was '-form to be of the order of 5 or10 seconds. Consequently, separate time scales were used for thetwo parts of the record shown in fi;tires 1(a) and 1(b) . The record-was terminated when the pilot, who was fl y ing under the hood, removedhis goggles at an altitude of about 150 feet and at a positionapproximately 2000 feet from the end of the runway.

DISCUSSION

AlthouQ figure 1 is a record of only one approach, this figureshows results that are typical of those obtained from all the approachesmade. Before these approaches were nade, it was thought that pilots::Might be afraid to bars': and. would ma-.e all heeding_ corrections bysideslippin6 in flat turns made by uce of the rudder. However, itwas found that the pilots always flew the _:.irplane in the normal manner;that is, left rudder was coordinated with left aileron and right rudderwas coord_i nested with right aileron when makin6 left and right turns,recp_ ect _ y3ly. Exa:-roles o:i this coordination may be found at 32, 42,and 50 seconds in the illustrative time history of figure 1(a), andat 42, 52, and 100 seconds in the part of the time history in figure 1(b) .An examination of figure 1 and records of all the other blind approachesmade showed that the maneuvers never required the a Dlication of morethan +10 0 total aileron. 00 rudder ; and 00 elevator control. Thetotal control defections available were *25 0 total aileron; KO O rudder;and 250 up ; 100 down elevator. By reasonably exact coordination ofthe rudder and aileron controls ; the angles of sideslip were heldwithin =2 o of zero. Therefore, it appears that pilots normallycoordinate the rudder and aileron controls when ma'_:ing blind landingapproaches.

It was opparent from the force records that the pilot did consider-able physical wort by continually feeling out the friction in the controlsystem although he did not move the controls ver: far. The controlfriction on the ground was =14 wounds for the elevators, +13 poundsfor the ailerons, and i'20 mounds for the rudder. These friction forceswere considered oxcessive and were caused in large measure by thehydraulically oDerate3 automatic-Dilot servounits which contributedabout t10 ?pounds friction to each control system.

NACA RM No. L71720

3

CnITCTUDING REPiA

From these tests it appears that compliance with the presentIACA handling-qualities requirements will be sufficient to insurethat the stability and control characteristics of an airplane inblind landin` approaches will be satisfactory.

Langley Menprial Aeronautical LaboratorZ,National Advisory Committee for Aeronautics

Langley Field, Va.

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NACA RM No. L7F20

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