Cruise speed way too high?

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Syzygy
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Cruise speed way too high?

Post by Syzygy »

Hi, I've been flying the 182 in a variety of conditions and I've consistently seen cruise speeds way a ive book. Example flight: 2500 ft, 6° C, 29.85 inHg... 23"/2300 RPM and mixture rich: 145 KIAS. Book says it should be 133. Ideas as to why?

km2727
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Re: Cruise speed way too high?

Post by km2727 »

Hi Syzygy, I believe the book numbers your looking at are based on a gross weight of 3100 pounds and mixture leaned to "peak EGT" not "mixture rich". And also the speed given is KTAS not KIAS. But even then, may vary due to numerous factors such as condition of the plane and engine. Most times I get pretty close to or just slightly better than book numbers.
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mallcott
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Re: Cruise speed way too high?

Post by mallcott »

Syzygy wrote:Hi, I've been flying the 182 in a variety of conditions and I've consistently seen cruise speeds way a ive book. Example flight: 2500 ft, 6° C, 29.85 inHg... 23"/2300 RPM and mixture rich: 145 KIAS. Book says it should be 133. Ideas as to why?
There are a number of speed options for the 182. Can you tell us what configuration you are operating in?

Syzygy
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Re: Cruise speed way too high?

Post by Syzygy »

Thanks for the tips about speed options and weight. I increased to max gross weight and removed all fairings and my cruise speed at 2000 feet pressure altitude and ISA, 2300/23", is 130 knots, which is 3 knots below book. I re-added all fairings and kept conditions otherwise the same, and cruise speed increased to 140 knots, right at Vno. I'm not so prolific a 182 pilot in real life to know how much a difference the wheel and flap gap fairings make, but in the sim it's quite significant!

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mallcott
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Re: Cruise speed way too high?

Post by mallcott »

Syzygy wrote:Thanks for the tips about speed options and weight. I increased to max gross weight and removed all fairings and my cruise speed at 2000 feet pressure altitude and ISA, 2300/23", is 130 knots, which is 3 knots below book. I re-added all fairings and kept conditions otherwise the same, and cruise speed increased to 140 knots, right at Vno. I'm not so prolific a 182 pilot in real life to know how much a difference the wheel and flap gap fairings make, but in the sim it's quite significant!
It is similar, if not almost identical, in real life. Otherwise no-one would buy them or use them. They add weight, so if that is not offset by increased performance of a reasonable amount, the business model wouldn't make any sense (which explains why Cessna don't fit them as standard)


However, as noted, in real life there are a myriad of other factors that can , and do, affect performance. You didn't mention the prop, yet this and gap seals make a substantial difference, so do try all the combinations.

From there you will deduce that the performance of the sim aircraft brackets quoted specs (which are not necessarily accurate even though they may come from a manufacturer) as the real world manuals also reflect individual build variation. The difference between 130 and 140 is only 7% variation which is WELL within manufacturers guidelines, so it's really a non-issue. But if you're an owner that needs that extra ten knots, its value for money.

I flew two different Diamond Katana DA20 s with identical Rotax 80-horse engines:Same prop, similar ages and TT. One was consistently 10 knots faster on a given power setting than the other. Yet the `slow` one always felt more lively when getting off the ground. Just a matter of rigging. One of the variations that I'd love to see on a future A2A Accusim light aircraft project as it is so crucial in the actual flying world yet never properly represented in the sim.

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