NASA Technical Memorandum 104327

F/A-18A Inlet Flow Characteristics

During Maneuvers with Rapidly

Changing Angle of Attack

Andrew J. Yuhas, William G. Steenken, John G. Williams

and Kevin R. Walsh

NASA Contract NAS 3-26617

June 1997

National Aeronautics and

Space Administration

NASATechnicalMemorandum104327

F/A-18A Inlet Flow Characteristics

During Maneuvers with Rapidly

Changing Angle of Attack

Andrew J. Yuhas

Analytical Services & Materials, Inc.

Edwards, California

William G. Steenken and John G. Williams

General Electric Aircraft Engines

Cincinnati, Ohio

Kevin R. Walsh

NASA Dryden Flight Research Center

Edwards, Cafifornia

Under NASA Dryden Flight Research Center

Contract NAS 3-26617

1997

National Aeronautics and

Space Administration

Dryden Flight Research Center

Edwards, California 93523-0273

Background

• Inlet/engine compatibility

- Inlet evaluation at steady aerodynamic conditions is the cornerstone of inlet/engine

compatibility

- Peak distortion descriptors are determined over a finite time span

at fixed aerodynamic conditions

- Wind tunnel testing is the primary data source of inlet assessments

• Test configuration constraints

- Fixed model position

- Model-to-wind-tunnel size can limit AOA range

- Limited maneuvering capability - slow rates

• New high AOA capabilities

- Increased operating range of AOA and AOSS

- Increased aircraft maneuvering rates

Current inlet/engine compatibility testing separately determines inlet distortion generation

and engine distortion tolerance characteristics during wind tunnel testing. The goal is to determine

the inlet's pressure profiles at peak engine stall margin loss. The inlet evaluation is performed

using wind tunnels. In general, wind tunnel test conditions consist of a matrix of discrete, steady

aerodynamic conditions defined by Mach number, angle-of-attack (AOA), angle-of-sideslip

(AOSS), and airflow. Testing is conducted at fixed model positions. Wind tunnel and aircraft

model size can constrain assessments at high AOA. Maneuvering capability is limited to slow

rates. The introduction of new high AOA capabilities are increasing aircraft maneuvering rates

and the operating range of AOA and AOSS.
Objective

• Determine whether current practice is adequate in

describing inlet-generated total-pressure-distortion levels

during maneuvers with rapidly changing AOA

- Are distortion levels elevated during dynamic maneuvers?

- Any limitations with steady aerodynamic condition testing?

• Flight test assessment required

The objective of these analyses was to determine whether results obtained for steady

aerodynamic conditions were adequate for describing the inlet-generated total pressure distortion

levels that occur during rapid aircraft maneuvers. The evaluation focused on whether the

constrained steady aerodynamic condition test matrix describes inlet trends in sufficient detail as

currently practiced. If examination of the rapid maneuver results at any condition shows a

significant increase in peak level distortion when compared with the steady-aerodynamicconditions results, the inlet data would be analyzed to determine the source of these increased

peak distortion levels. The effects of dynamic AOA maneuvers on inlet distortion levels could

only be assessed during flight tests.
Aircraft/inlet/engine

• Aircraft

- NASA F/A-18A High Alpha

Research Vehicle with

thrust vectoring paddles

• Inlet

- Fixed geometry, side fuselage

mounted, single ramp, external

compression inlet

- Right-hand inlet used

• Engine

- General Electric F404-GE-400

afterburning turbofan engine

HARV right-hand inlet

High alpha inlet research data were obtained using the NASA High Alpha Research Vehicle

(HARV) at the NASA Dryden Flight Research Center. The aircraft is a preproduction F/A-18A

with an externally-mounted thrust-vectoring paddle system. This modification allows the aircraft

to fly at sustained high AOA conditions. The aircraft's inlet is a fixed geometry, side fuselage

mounted, single ramp, external compression inlet. A pair of General Electric F404-GE-400

afterburning turbofan engines are installed in the aircraft. All inlet research testing was conducted

using the right inlet/engine combination (aft-looking-forward).
Inlet total-pressure measurements

• Descriptors defined from inlet

rake measurements

• Inlet rake measurements

- 40 measurement probes

- 5 rings with 8 equally-spaced

circumferential positions

- High-response, absolute

pressures with no significant

time lag (2143 sps)

• Acquisition of data conforms

to Society of Automotive Engineers

ARP 1420 standards

HARV inlet rake

with circumferential rings

superimposed

The inlet distortion descriptors require measurements from an inlet rake. The standard rake

configuration is a 40-probe array consisting of eight equiangularly spaced rakes with five ports

per rake located at the centroids of equal areas. This array provides 5 rings with 8 equally-spaced

circumferential pressures. The HARV inlet rake provided high-frequency-response, absolute

pressures with no significant timelag. This was a requirement for the dynamic maneuver

assessment. Data recording was performed at 2143 samples per second. The acquisition of data

conformed with the Society of Automotive Engineers Aerospace-Recommended-Practice (ARP)

1420 standards for total-pressure-distortion measurement.

4
In let total-pressu re-distortion descriptors

• Inlet recovery

- Face average total pressure referenced to the freestream

total pressure

• General Electric F404 distortion methodology

• Dynamic circumferential distortion

- Time-variant magnitude

of the low-pressure defect

for each ring (5 rings)

- Average adjacent

rings (4 calculated rings)

- Select maximum value for

one of the 4 averaged rings

Ring-probe

total

pressure

Circumferential distortion

__ fRingW'pressuredefect

e

_ Minimum ring pressure

0 360

Circumferential location, deg

This inlet research assessment used three inlet descriptors: inlet recovery, peak dynamic

circumferential distortion, and peak dynamic radial distortion. Inlet recovery is defined as the face

average pressure referenced to the freestream total pressure. The distortion descriptors used the

General Electric F404 distortion methodology. Dynamic circumferential distortion is defined as

the overall maximum value of adjacently-averaged rings of the time-variant magnitude of the

low-pressure defect for each ring.

5
Inlet total-pressure-distortion descriptors

• Dynamic radial distortion

- Time-variant magnitude of the difference between

the ring average pressure and the face average

pressure for the tip and hub ring (2 rings)

- Select maximum value of either ring

° Peak value determination of circumferential

and radial descriptors

- Maximum observed magnitude computed for

a finite period of time at steady aerodynamic conditions

- Randomness of pressure fluctuations in an inlet

requires a statistically significant data sample

- HARV steady data used 4-6 sec

Dynamic radial distortion is defined as the maximum value of either the tip or hub ring for the

time-variant magnitude of the difference between the ring average pressure and the face average

pressure. The circumferential and radial distortion descriptors are both referenced to the face

average pressure. The circumferential and radial distortion descriptors require further reduction to

determine their peak values. For steady aerodynamic conditions, the maximum observed

magnitude is determined over a finite period of time. This time period needs to be a statistically

significant period because of the randomness of inlet pressure fluctuations. The HARV steady

aerodynamic conditions were held to obtain a 4 to 6 second data sample.

6
Test matrix

• Steady aerodynamic conditions

- 79 conditions at maximum corrected airflow of 144 Ib/sec

- Mach 0.3 and 0.4

- -10 ° to 60° AOA and -8 ° to 12° AOSS

• Rapid AOA maneuvers

- 46 maneuvers at maximum corrected airflow of 144 Ib/sec

- Initial conditions

• 10°, 25-30 °, and 60° AOA at 0°, _5° AOSS (Mach 0.3)

• 10°, 12-15 °, and 40° AOA at 0°, +5 ° AOSS (Mach 0.4)

- AOA sweeps

• Low-to-high AOA, 46 deg/sec maximum rate

• High-to-low AOA, -37 deg/sec maximum rate

Two databases were required for this research: one based on steady aerodynamic conditions

and the other using rapid AOA maneuvers. In brief, the steady aerodynamic conditions consisted

of 79 test points at Mach 0.3 and 0.4 with AOA from -10 ° to 60 ° and AOSS from -8 ° to +12 °.

Conditions typically were held for 6 seconds. The rapid AOA maneuvers consisted of

46 maneuvers. The initial setup (at steady aerodynamic conditions) was, for Mach 0.3 at 10 °,

25-30 °, and 60 ° AOA with 0 ° and _+5° AOSS; and for Mach 0.4 at 10 °, 12-15 °, and 40 ° AOA

with 0 ° and +5 ° AOSS. Once the initial steady conditions were held for 2 to 3 seconds, the

dynamic maneuver was performed. Both positive and negative AOA rates were performed with

maximum rates of-37 deg/sec and 46 deg/sec being attained. Both databases required that the

engine be held at maximum corrected airflow of about 144 lb/sec.
Test matrix

• Comparison of steady aerodynamic conditions and dynamic AOA

maneuvers envelope at Mach 0.3

AOA, deg

70

60

50

40

30

20

10

0

-10

-20

-15

........... :........... :.... .".._ .-..-

_euver envelope

,_y.J_.,__... Comparison boundary

//////.11 ', i

_,_,k'_._¢_'t l' ' -"_ Steady estimation envelope

' A-{.... .......

-10 -5 0 5 10 15

AOSS, deg

This AOA-AOSS envelope shows the extent of the comparisons performed in this study.

Three envelopes are shown for the Mach 0.3 database. The first envelope is the steady

aerodynamic estimation envelope with limits at about -10 ° to 60 ° AOA and +10 ° AOSS. The

second envelope is the dynamic maneuver envelope which shows the extent of the AOA-AOSS

excursions reached during maneuvers. The intersection of these two envelopes forms the third

envelope and shows the extent of the comparison performed at the Mach 0.3 conditions. A similar

set of envelopes exists for the Mach 0.4 database with an upper AOA limit near 40 °.
Analysis

• Steady aerodynamic conditions

- Inlet characteristics processed, peak values found,

and models created

- Reduced to tabular format

- Function of AOA, AOSS, and Mach number

• Dynamic maneuvers

- Time-variant inlet characteristics calculated

- Airdata analyzed to remove measurement errors

• Dynamic Aircraft Maneuvers Program (DAMP)

- Computes descriptors based on steady aerodynamic

conditions for comparison with dynamic maneuver

values at equivalent conditions

Each database was analyzed in order for calculations and comparisons to be performed. For

each aerodynamic condition inlet descriptors were calculated. These descriptors included average

recovery and peak distortion values. Further analysis reduced these data into tabular format which

provided each descriptor as a function of AOA, AOSS, and Mach number.

Each dynamic maneuver had the time-variant inlet characteristics calculated. Special data

review was performed to remove any known measurement errors from the AOA and AOSS

signals. These errors included the effects of wing bending frequency on the airdata wing-tipmounted vanes and the averaging of divergent AOSS vanes at high AOA (greater than 60°).

A computer program called the Dynamic Aircraft Maneuvers Program (DAMP) was written

to compute inlet recovery and peak distortion descriptors based on steady aerodynamic conditions

for comparison with dynamic maneuver values at equivalent conditions.

9
Low-to-high AOA sweep at Mach 0.3

70_

AOA, deg

i

60 = = " ' ------------_

...................::.................!...................'_.................'_................ _i_i

i Ii , ,

50 ................... •................... ::............. Dynamic portion

................... ',................... :................... _ ...................................

40 ................... _................... i................... ;.................. ' .................

L

,,

................... =....................................... ,' ................ ,'..................

30_................................ ==.............................. i................

20 Steady portion ..........

lo ............ , ---,.............._ ................_..................

,, ,,

.................. "................... i................... ,_.................. ,_..................

0 .................. "................... :................... ".................. i..................

.................. "................... i................... _-.................. ,_..................

-10 ' '

0 1 2 3 4 5

Time, sec

This figure shows a rapid AOA maneuver, a low-to-high AOA sweep at Mach 0.3. The initial

steady portion is at 10 ° AOA, and is immediately followed by the dynamic portion with AOA

going beyond 60 °. The maximum AOA rate for this maneuver was approximately 30 deg/sec.

This maneuver will be used to describe the inlet descriptor comparisons in this presentation.

10
Inlet recovery comparison at high AOA

Inlet

recovery

Dynamic

maneuver

inlet

recovery

o.981

o.961

0.941

0.921

o.9oi

0.98

0.96

0.94

0.92

0.90

0.88

0.86

;=='_-z,z5--;.crzcc,,-_'7.c,:.:,::_;,-=:-a---.azL'_.:,._=a_;;==- ' ;...... i .................

................. _ ................ r ................ T .......... n .................

................. L-................ L ................ _. ...............................

................. ,'_................ ,_................ _ _................ I ...............

................. r ................ r ..... , ..........

................. L ................ L ..........

................. "................ i..... recovery at 55 ° AOA ----_--:_,--

.... -- Dynamic .......... ".................. J.............. . .......... _

.... _ _t_y .......... F ................ r ................................

.................................. L ................ _ .................................

0 1 2 3 4 5

Time, sec

; i _ ; , i

, i _ , ,

..... _ ...................... L ........... i........... L .......... J ...... i .......

, , i i , ,

I i , I i

i i i , I

I B I , i i

, , ,, , , ,

..... •........... ,........... •........ ,-.......... •........... _...........

i , i i ,

..... z ........... ,........ ,........... L .......... J ........... L ...........

i r , i i i

i , i i i

i i t i i i

, i 0 J i

+1 '/oagreement band :

0.86 0.88 0.90 0.92 0.94 0.96 0.98

Steady-aerodynamic-estimation inlet recovery

The inlet recovery characteristics during a dynamic AOA sweep are compared with the steady

aerodynamic estimation. The top plot compares the recovery level for the dynamic maneuver to

the estimation from the steady aerodynamic conditions. The trends show good agreement. A

sudden change in the recovery at about 55 ° AOA does occur. It is believed to be caused by a

change in the inlet flow-separation regions. The bottom plot performs a direct comparison

between the recovery levels of steady estimation and the dynamic maneuver. A +_1% agreement

band about the line of perfect agreement demonstrates the strong agreement between the

estimated and measured recovery levels.

11
Peak circumferential distortion comparison at high AOA

Circumferential

distortion

AOA, deg

0.20. i i ........... LP.eak.va mes_f_rp_r__ steady_........

lestimation model _ . .-' 0.16 ! Dynamic maneuver peaks ....................................... _:__

show agreement with steady : : -_.-

" estimation dur ng steady port on -D_n-c_.m'c;in'l_-_-u_/(_r_-!---_ -_-'-'' .... ---. 0.121 ..................................... _

, , , , -_ ,-._,,llil

................. i................ p ................ IT............. _--_, -- -- ' : t

0.041 ........ •................

_ Dynamic maneuv, .,'_

0.00 I _ I • _ peaks are lower /

o 1 2 3 than the steady /

Time sec estimation during I

70 dynamic portior ]i i i

60 _

50;

40

30

20

10

0

i

i i i i

- Mach ,,.,, --, ................. ,-................ T................ -,..............

J i t t

__________,,,___.

................. I................. r ................ r .............................. ._,,'_-- - - - - - - - -

i i i

i i i

i i , i

................. r................. r ................ r ............... -r ................

................. !,................. ', _.b................ _.............. 4!,................

t t t t

0 1 2 3 4 5

Time, sec

The circumferential distortion levels during a dynamic AOA sweep are compared with the

peak estimation from steady aerodynamic conditions. The top plot shows the actual distortion

levels while the bottom plot shows the AOA trace from 10° to 62 ° AOA. The distortion levels

show the expected increase in the level and activity of distortion as higher AOA is reached. The

peaks in the circumferential distortion levels for the transient portions of the dynamic maneuver

are less than those of the steady aerodynamic estimation model. This was true for all excursions

into the high AOA region of 30 ° to 62 °.

12
Peak radial distortion comparison at high AOA

Radial

distortion

AOA, deg

0.12

0.101

0.081

0.06_

0.041

0.02

0.00

Dynamic maneuver peaks I , ;

show agreement with steady I _Peak values f_,om steady

estimation during steady portion I.............. i e-sti-rna-ti()n-_'l-o_el--,_- _._'"

.................. _................ I "---:.............. L.................. L........ :-,_--" ..... I I • I I ,."

,, _ ,, Dynamic,, maneuver_ : ....--- _|lI_J_

! Dynamic maneuver

peaks are lower

0 1 2 3 thanthesteady

Time, sec estimation during

70

60 -

50"

40 -

30 :

20:

10-

0

0

• . dynamic portion

/

..MachO._._.................. -.................. i.................. ,_............ 7"

.................. ".................. !................... r.................. _.... :_ ........

.................. i.................. ".................. _...........................

.............. 12122----i1512 ............. , ii,1511 iiiiii ii

I I i

2 3 4 5

Time, sec

The radial distortion levels during a dynamic AOA sweep are compared to the peak

estimation from steady aerodynamic conditions. Again, the top plot shows the actual distortion

levels while the bottom plot shows the AOA trace from 10 ° to 62 ° AOA. The peak radial

distortion levels for the transient portions of the dynamic maneuver are less than those of the

steady aerodynamic estimation model. This was true for all excursions into the high AOA

region of 30 ° to 62 ° . The steady estimation peak levels of radial distortion tended to be

approximately 0.01 to 0.03 higher than the peak levels obtained during dynamic maneuvers.

13
Peak circumferential distortion comparison at low AOA

Circumferential

distortion

AOA and

AOSS, deg

0.20

0.16

0.12

0.08

0.04

0.00

.,: LEX-gen'erated .',

........................... ir............ flow disturbance ........ I/ .............

Peakvaluesfromjsteady_ .... , _.._'_.___i

--_i,-ti_-_,,,_-_-i..i..,-6-a _r-_........._--",_.......i.................. -'_-i .............

............. -a. .... _,..... _ ..... ,-_ I I

' • .. ..... L ............. "- -._ ........................ . " - .......

0 2 4 6

40 Time, sec

3O

2O

10

0

-10

Mach 0,3 i !

.............. :_____:.__.:........... AOA ; ', ........ _.......................... _ .............

........................... i................................... i........ -/

,, ! , j

........................... i.......................... i....... ......

0 2 4 6

Time, sec

This figure shows the circumferential distortion levels during a dynamic AOA sweep into the

low AOA region of 0 ° to 4 °. As before, the top plot shows the distortion levels while the bottom

plot shows the AOA trace from 30 ° to 0 ° to 25 ° AOA. The dynamic maneuver was also performed

starting from -5 ° AOSS. The circumferential distortion levels of the dynamic maneuver exceeded

the steady aerodynamic estimation at 0 ° to 2 ° AOA. It was clear that the discrete steadyaerodynamic conditions did not provide a sufficiently detailed description of the inlet behavior

during this maneuver. The ingestion of a LEX-generated flow disturbance is believed to be a factor

contributing to the elevated levels. This result was noted in a number of low AOA sweeps at

Mach 0.3 and 0.4. The greatest difference seen for the entire database was 0.05.

14
Results

• Inlet recovery comparison

- Dynamic maneuver values were typically within _+1%

of those at steady aerodynamic conditions

- Discrete changes in recovery trend at high AOA

noted during dynamic maneuvers, possibly

associated with changing inlet separation regions

For inlet recovery comparisons:

1. Within the AOA/AOSS model boundary conditions, the majority of inlet recovery levels for

the dynamic AOA maneuvers are within +0.01 of the steady aerodynamic model estimations.

. The dynamic maneuver data exhibit discrete changes in the recovery trends in the vicinity

of 50 ° to 60 ° AOA at Mach 0.3 and 40 ° AOA at Mach 0.4, during low to high AOA sweeps.

At these conditions, the steady aerodynamic model overpredicts the inlet recovery level.

The inlet recovery change is associated with an increase in dynamic activity and changes

in the circumferential distortion trend. These changes require further investigation. The

associated behavior of the inlet lip and throat pressures will be examined.

15
Results (continued)

• Peak circumferential distortion comparison

- At high AOA (30 ° to 62°), dynamic maneuver levels

were less than or equal to steady aerodynamic estimations

- At low AOA (-6 ° to 4°), dynamic maneuver levels

exceeded the steady aerodynamic estimations

by as much as 0.05 (or 5%)

- LEX-generated flow disturbance is a possible factor

at low AOA

For peak circumferential distortion comparisons:

° At high AOA conditions (30 ° to 62°), the peak circumferential distortion levels for the

transient portions of any dynamic maneuver are less than or equal to those of the steady

aerodynamic estimation model. The trends in the peak distortion levels are consistent

between the dynamic maneuvers and the steady aerodynamic estimation model.

. At low AOA (-6 ° to 4°), during high-to-low AOA maneuvers, the dynamic-maneuver peak

circumferential distortion levels exceeded those of the steady aerodynamic estimation

model, especially at Mach 0.4. It was clear that the discrete steady-aerodynamic conditions

did not provide a sufficiently detailed description of the inlet behavior during these

maneuvers. A LEX-generated flow disturbance is thought to be a factor.

3. The maximum peak value of the circumferential distortion during dynamic AOA maneuvers

relative to the steady aerodynamic estimation model was 0.05 at less than 4 ° AOA.

16
Results (continued)

° Peak radial distortion comparison

- At high AOA (30° to 62°), the dynamic maneuver

levels were less than the steady aerodynamic estimations

- At low AOA (--6° to 4°), the dynamic maneuver levels

slightly exceeded the steady aerodynamic estimations

by less than 0.01 (or 1%)

For peak radial distortion comparisons:

. At high AOA conditions (30 ° to 62°), the peak radial distortion levels for the transient

portion of any dynamic maneuvers are less than those of the steady aerodynamic

estimation model. The peak radial distortion of the steady aerodynamic model was

estimated to be 0.01-0.03 higher than the dynamic maneuvers.

. At low AOA conditions (-6 ° to 4°), during high-to-low AOA maneuvers, the dynamicmaneuver peak radial distortion levels slightly exceeded those of the steady aerodynamic

estimation model by less than 0.01 at Mach 0.4 (not shown in presentation).

17
Concluding remarks

• No evidence of peak inlet distortion levels being elevated

by dynamic maneuver conditions at high AOA (30° to 62°)

compared with steady aerodynamic estimations

• During sweeps to high AOA, dynamic maneuver distortion

levels rarely rose to steady aerodynamic peak estimations

• Dynamic maneuvers effective at identifying conditions

where discrete changes in inlet behavior occur

- Propagation of separated flow region

- Possible LEX-generated flow disturbance

Concluding remarks:

. There was no evidence that peak inlet distortion levels were being elevated by dynamic

maneuver conditions when compared to those at steady aerodynamic estimations at

equivalent vehicle attitudes for high AOA conditions (30 ° to 62°).

2. During attitude changes to high AOA, the circumferential and radial distortion values rarely

rose to values obtained during maneuvers with steady aerodynamic conditions.

. Dynamic aircraft maneuvers were effective at characterizing elevated circumferential

distortion levels where a LEX-generated flow disturbance may have occurred. Such

disturbances could not be verified by other means.

18

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1. AGENCY USE ONLY (Leave blank) 2. REPORT DATE 3. REPORTTYPE AND DATES COVERED

June 1997 Technical Memorandum

4.TITLE AND SUBTITLE 5. FUNDING NUMBERS

F/A-18A Inlet Flow Characteristics During Maneuvers with Rapidly

Changing Angle of Attack

6. AUTHOR(S) WU 505-68-30

Andrew J. Yuhas, William G. Steenken, John G. Williams,

and Kevin R. Walsh

7.PERFORMINGORGANIZATIONNAME(S) ANDADDRESS(ES)

Analytical Services & Materials, Inc.

Edwards, California

General Electric Aircraft Engines

Cincinnati, Ohio

9.SPONSORING/MONITORING AGENCYNAME(S)ANDADDRESS(ES)

NASA Dryden Flight Research Facility

EO. Box 273

Edwards, California 93523-0273

8. PERFORMING ORGANIZATION

REPORT NUMBER

H-2146

10. SPONSORING/MONITORING

AGENCY REPORT NUMBER

NASA TM- 104327

NASA Contract NAS 3-26617

11. SUPPLEMENTARY NOTES

Oral presentation presented at the NASA High Angle-of-Attack Technology Conference, Inlet Aerodynamics

and Propulsion Session, NASA Langley Research Center, September 17-19, 1996, Hampton, Virginia.

12a. DISTRIBUTION/AVAILABILITY STATEMENT

Unclassified--Unlimited

Subject Category 07

12b. DISTRIBUTION CODE

13. ABSTRACT (Maximum 200 words)

The performance and distortion levels of the right inlet of the F/A-18A High Alpha Research Vehicle were

assessed during maneuvers with rapidly changing angle-of-attack at the NASA Dryden Flight Research

Center, Edwards, California. The distortion levels were compared with those produced by current inletengine compatibility evaluation techniques. The objective of these analyses was to determine whether the

results obtained for steady aerodynamic conditions were adequate to describe the inlet-generated distortion

levels that occur during rapid aircraft maneuvers. The test data were obtained during 46 dynamic maneuvers at

Mach numbers of 0.3 and 0.4. Levels of inlet recovery, peak dynamic circumferential distortion, and peak

dynamic radial distortion of dynamic maneuvers for a General Electric F404-GE-400 turbofan engine were

compared with estimations based on steady aerodynamic conditions. The comparisons were performed at

equivalent angle-of-attack, angle-of-sideslip, and Mach number. Results showed no evidence of peak inlet

distortion levels being elevated by dynamic maneuver conditions at high angle-of-attack compared with

steady aerodynamic estimations. During sweeps into high angle-of-attack, the peak distortion levels of the

dynamic maneuvers rarely rose to steady aerodynamic estimations. The dynamic maneuvers were shown to be

effective at identifying conditions when discrete changes in inlet behavior occur.

14. SUBJECTTERMS

Comparison to steady aerodynamic conditions, F/A-18A aircraft, High angle of

attack, Inlet distortion, Rapid angle-of-attack maneuvers

17. SECURITY CLASSIFICATION 18. SECURITY CLASSIFICATION 19. SECURITY CLASSIFICATION

OF REPORT OFTHIS PAGE OF ABSTRACT

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