# FLFACT

Bulk Data Entry Used to specify the aerodynamic factors in aerodynamic flutter analysis.

The aerodynamic factors are:
• Density ratios
• Mach numbers
• Reduced frequencies
• Velocities

## Format 1

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
FLFACT ID F1 F2 F3 F4 F5 F6 F7
F8 F9 etc. etc. etc.

## Format 2

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
FLFACT ID F1 THRU FNF NF FMID

## Example 1

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
FLFACT 1002 0.1 0.56 1.01 4.0

## Example 2

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
FLFACT 1003 0.120 THRU 0.550 10 0.26

## Definitions

Field Contents SI Unit Example
ID Unique identification number.

No default (Integer > 0)

Fi Aerodynamic factor value.
Format 1
List of aerodynamic factors.
Format 2
Only F1 needs to be specified and it is the value of the first aerodynamic factor.

No default (Real)

FNF Final aerodynamic factor value.

Required when Format 2 is used.

No default (Real)

NF Number of aerodynamic factors.

Required when Format 2 is used.

No default (Integer > 0)

FMID Intermediate aerodynamic factor value. 5 6

Required when Format 2 is used.

No default (Real)

1. The FLFACT Bulk Data Entry must be referenced by a FLUTTER Bulk Data Entry. Unreferenced FLFACT entries will be ignored during the analysis.
2. Multiple FLFACT entries can point to the same FLUTTER Bulk Data Entry.
3. Each FLFACT entry must contain data of only one type of aerodynamic factor.
4. The order of the factors in the FLFACT entries determines the order in which they will be used withing the looping of aerodynamic flutter analysis.
5. When Format 2 is used, FMID must lie between F1 and FNF.(1)
$\frac{F1\left(FNF-FMID\right)\left(NF-i\right)+FNF\left(FMID-F1\right)\left(i-1\right)}{\left(FNF-FMID\right)\left(NF-i\right)+\left(FMID-F1\right)\left(i-1\right)}$

Where, $i$ = 1, 2, …, NF.

6. When Format 2 is used, the value of FMID determines the distribution of the factors.
• If FMID = $\frac{\left(F1+FNF\right)}{2}$ , the factors are equally distributed between F1 and FNF.
• Otherwise, the factors are unequally distributed and will be concentrated around FMID.
7. If METHOD = PK in the FLUTTER definition and if a FLFACT is used to specify velocities, then the velocities must be non-zero.
8. If METHOD = PK or PKNL in the FLUTTER definition:
• Entering negative values produces eigenvector results at a velocity equal to the positive value of the input.
• Entering positive values produces eigenvalue results without eigenvectors.