Systems consist of single duct system with two sets of reaction control nozzles, one linked mechanically to pilot's controls, and other set driven by electric servomotors commanded by preselected combinations of electrical signals

Pauli, F. A.

English

NASA Technical Reports Server

•	
June 1971	 Brief 71-10202 
NASA TECH BRIEF 
Ames Research Center 
•TI	 iiiITi	 -_!-i±i - 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage 
commercial application. Tech Briefs are available on a subscription basis from the National Technical Information 
Service, Springfield, Virginia 22151. Requests for individual copies or questions relating to the Tech Brief program may 
be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
_--
Attitude Controls for VTOL Aircraft 
.
The attitude-control jet nozzles of a VTOL aircraft 
may be operated by mechanical connection to the 
pilot's control stick and pedals. However, it is desir-. 
able and often necessary to increase the flexibility of 
the attitude control system by incorporating an eléc-
trically-controlled set of nozzles operated by servo-
motors. Thus, the attitude control systems currently 
in use consist of a single duct system with two sets of 
reaction control nozzles, one linked mechanically to 
the pilot's controls, and the other set driven by elec-
tric servomotors which are commanded by preselected 
combinations of electrical signals generated by the 
pilot, rate gyros, or other signal sources. In such sys-
tems, the range of forces available for attitude control 
is only a portion of that provided by the compressed 
air source, because air is ejected from both sets of 
nozzles at all times even though only one set is being 
used for control. Moreover, the outputs of the me-
chanically-controlled and the electrically-actuated 
nozzles produce independent forces which may be 
additive or may work in conflict; when the forces are 
in conflict, there is little effective control power avail-
able to the pilot, and when they are additive, the 
amount of control input required for a given attitude 
maneuver will often require* unexpectedly small pilot 
corrective actions.. 
It is obviously desirable to provide the pilot with 
the capability of deactivating completely either the 
electrically- or the mechanically-controlled system. 
However, the electrically-controlled servo systems 
that are currently employed require that the mechan-
ically-controlled nozzles be inactivated either by phys-
ically disconnecting them from the pilot-operated 
controls or by using complicated systems for combin-
ing the two modes of operation. Moreover, since the
time required to effect any changeover in the current 
systems is altogether too long to permit the pilot to 
switch from one mode of operation to the other in 
emergencies, and there is a reluctance of the pilot to 
depend on all-electric systems, it became necessary 
to seek an improved attitude control system. 
The improved attitude control system developed 
for VTOL aircraft consists of two air distribution 
systems, one with electrically- and the other 
(continued overleaf) 
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mechanically-controlled jet nozzles which may be op-
erated selectively from the same pilot input without 
interference. Moreover, if the mechanical system has 
been inactivated, it will be automatically reactivated 
upon failure of the electrical control system. 
The system employs two sets of reaction nozzles 
which are displaced from various axes of the aircraft. 
Each set is fed by a separate duct system selectively 
connected to a source of gas under pressure, prefer-
ably bled off from a jet engine. For control about 
each orthogonal axis, nozzles of the first set (Nm) are 
controlled mechanically and nozzles of the second set 
(Ne) are controlled electrically by servo motors (see 
diagram). 
A dual butterfly valve, interposed between the air 
supply duct and the ducts feeding the separate sys-
tems, is movable within less than one second into the 
position Which will supply either system exclusively 
of the other. The valve is latched electrically in the 
electrical control position, and a spring biases the 
valve disc assembly so that the mechanically-control, 
led nozzles are placed into communication with their 
feed line if electrical power is interrupted. Hence, 
the attitude control system is returned to mechanical 
control immediately at the option of the pilot or by 
the failure of the electrical system. Since only one set 
of nozzles is operated at a given time, the full control 
force derivable from the compressed gas source can 
be applied to the control nozzles.
Notes: 
1. The following documentation is available from: 
National Technical Information Service 
Operations Division 
Springfield, Virginia 22151 
Single document price $3.00 
(or microfiche $0.95) 
Reference: 
NASA TN D-5715 (N70-20725), A Reaction 
Attitude Control System for Jet VTOL 
Research Aircraft. 
2. No other documentation is available. Specific ques-
tions, however, may be directed to: 
Technology Utilization Officer 
Ames Research Center 
Moffett Field, California 94035 
Reference: B71-10202 
Patent status: 
This invention has been patented by NASA (U.S. 
Patent No. 3,472,470) and royalty-free license rights 
will be granted for its commercial development. In-
quiries about obtaining a license should be addressed 
to:
Patent Counsel 
Mail Code 200-I 1A 
Ames Research Center 
Moffett Field, California 94035 
Source: Frank A. Pauli

NASA - Ames Research Center

(XAC.8972)
. 
. 
. 
Brief 71-10202	
-	 Category 05


Attitude controls for VTOL aircraft

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