Author Topic: La7 speed at 13k is 10mph too fast (Read 1632 times)

Wilbus · « **Reply #15 on:** March 04, 2002, 11:45:23 AM »

RAM, would it be possible for you to send me some charts that you have? I am desperatly trying to find such things but without luck.

bozon · « **Reply #16 on:** March 04, 2002, 12:29:32 PM »

MANDOBLE,
if you are heavier, you need more lift to keep you in level flight. more lift means greater angle-of-attack, that means more drag for the same speed. at top speed, the effective (actually trasfered through the prop) power of the engine equals the rate of consumed energy by the drag. hence, max speed is lower.

Bozon

hitech · « **Reply #17 on:** March 04, 2002, 12:38:37 PM »

Where the weight is can also effect top speed.

The more nose heavy a plane ,the slower it is.

hitech · « **Reply #18 on:** March 04, 2002, 01:10:59 PM »

LA7 at 13k chart shows 393, chart can't be read this accuratly but the number we put in is 393.

Just ran the test at 13k full fuel, we hit 392

Zoom in on the gauge you will see it's very slightly below 400.

To make a long story short it's correct.

Btw thanks for the testing. If you wish to tests speeds the best way is with the .speed command

HiTech

Sombra · « **Reply #19 on:** March 04, 2002, 01:25:37 PM »

>analog gauges to a tolerance of 1 mph, you have eyes better than mine. From my experience, its hard to get an accurate reading within a plus or minus 5 mph tolerance.

A "debug" digital speed (etc) indicator would be a nice adition for end user, i think.

Greetings

Wilbus · « **Reply #20 on:** March 04, 2002, 01:35:31 PM »

Hitech, could you maybe, sometime in the future implant a Digital speed meter for offline use only? Just something to have in a corner of the picture, same thing with rate of climb and such, would make testing easier, and IF we find some misstakes, it would benifit everybody. Allso, people would do more testing and you'd hear less whining.

Btw, do you know which engine you have modelled for the Ta152?

thrila · « **Reply #21 on:** March 04, 2002, 02:20:52 PM »

.speed command....didn't know that cool!!!
Alright i'll give it a go with that HT.

For a moment i almost cancelled my whisky bribe to you HT;)

While you're in this thread HT, what engines have you modelled for the mossie fbVI? 21's? 25's? ......oh and ......errrr....any plans for any other mossie varients in the future.

FLS · « **Reply #22 on:** March 04, 2002, 03:31:44 PM »

At stall speeds induced drag is a greater part of the total drag force than parasitic drag but at max speeds induced drag is negligible and most of the total drag force comes from parasitic drag. The slight increase in AoA needed for the additional lift to balance the weight of 100% fuel vs 50% fuel at max speeds would add a little induced drag to the negligible induced drag component of the total drag.

In other words, you shouldn't see any significant speed difference at max level speed comparing 50% and 100% fuel loads.

If you use the .speed command keep in mind that it sets the IAS not TAS.

--)-FLS----
Musketeers

Apache · « **Reply #23 on:** March 04, 2002, 03:50:30 PM »

^ What him say?

R4M · « **Reply #24 on:** March 04, 2002, 04:14:49 PM »

Quote

Originally posted by Apache
^ What him say?

him say more fuel not affect top speed.

hitech · « **Reply #25 on:** March 04, 2002, 04:36:51 PM »

Just to be accurate

Him say 50% fuel will not effect top speed by a lot.

HoHun · « **Reply #26 on:** March 04, 2002, 04:51:47 PM »

Hi everyone,

Actually, more fuel might even make a fighter faster.

Design angle of incidence would typically be selected for top speed at full pressure altitude. Below this altitude, the fighter probably flies with a nose-down attitude, meaning that the fuselage is not optimally aligned with the airflow. More fuel and more weight means that the same lift is achieved at a higher angle of attack, which is equivalent to a less pronounced nose-down attitude of the fuselage and less parasitic drag.

If the decrease of parasitic drag is greater than the increase of induced drag, the heavier aircraft will be faster.

Regards,

Henning (HoHun)

MANDOBLE · « **Reply #27 on:** March 04, 2002, 06:00:01 PM »

Exactly HoHun.

Glasses · « **Reply #28 on:** March 04, 2002, 09:24:04 PM »

Too much aerodynamic information must stop reading threads must must.................

Zigrat · « **Reply #29 on:** March 04, 2002, 10:30:52 PM »

henning i believe you are on crack. your statements make no sense. fly at a higher angle of attack for the same lift? huh?

hitech is correct however asssuming aces high models trim drag. does it? the more stable a plane is (the greater the static margin) for a given airframe and weight the tail will have more required downfore to maintain zero pitching moment for cruise. i do not know if aces high calculates trim drag tho.