Quick descent in the connie. How????

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bobsk8
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Quick descent in the connie. How????

Post by bobsk8 »

I am still confused when descending in the Connie, or even slowing it down. If I am flying level at say 8,000 feet and try and slow down from cruise speed, I can lower the MP to say 18" and prop to 1800 rpm and it seems like the aircraft wants to cruise along at the same speed forever. Throw in even a very slight rate of descent, and it will actually accelerate. How on earth to you get this aircraft to slow down, and I would like some specific numbers rather than " just reduce MP and keep everything squared", which seems to accomplish very little.
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Artur
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Re: Quick descent in the connie. How????

Post by Artur »

I think there is nothing like "quick descent", the only way is to reduce MP below prop RPM...
I know the rule that prop should not drive engine, but seems there is no other way.
As long as speed will drop to first dot, deploy flaps, and from now on things are getting better

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Re: Quick descent in the connie. How????

Post by n421nj »

You need to do a test. Different weight and weather will change things. Once in cruise reduce power and wait and watch the gauges. As the plane slows down you will need more back pressure to maintain altitude which will translate into slower airspeed. Once you reach the speed in which you want to descend at, slowly start down. Use pitch to control airspeed. Take note of how long it takes from when you reduce power until the plane starts to slow. This will give u an idea of how to plan your descent
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Randall
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Re: Quick descent in the connie. How????

Post by Randall »

What I do is reduce the MAP to 22" and keep the RPM at the cruise setting, 2200 rpm.

If I descend at 500 fpm, the indicated airspeed goes up to around 200 knots. If I descend at 1,000 fpm, the speed goes up to around 230 - 235 knots. When reaching the desired atltiude, I keep the engine set at 22" and 2200 rpm, and fly level. This slows the plane down to flap speed.

I don't see anything wrong with an increase in airspeed on descent. I just plan ahead. Also, I never need to reduce power below 22" and 2200 rpm until approach, when I lower the MAP to 20". On short final I bring the props up to 2300 rpm.

I am certainly no expert, but it seems to me that extremely low MAP and RPM are neither necessary nor healthy for the engines. I also don't see any problem with an increase of airspeed in the descent, as long as the airspeed needle out of the yellow and red range.

With proper planning, this seems to work out fine. Some minor adjustments may need to be made for a significant headwind or tailwind.


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triflyman
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Re: Quick descent in the connie. How????

Post by triflyman »

Randall wrote:What I do is reduce the MAP to 22" and keep the RPM at the cruise setting, 2200 rpm.

If I descend at 500 fpm, the indicated airspeed goes up to around 200 knots. If I descend at 1,000 fpm, the speed goes up to around 230 - 235 knots. When reaching the desired atltiude, I keep the engine set at 22" and 2200 rpm, and fly level. This slows the plane down to flap speed.

I don't see anything wrong with an increase in airspeed on descent. I just plan ahead. Also, I never need to reduce power below 22" and 2200 rpm until approach, when I lower the MAP to 20". On short final I bring the props up to 2300 rpm.

I am certainly no expert, but it seems to me that extremely low MAP and RPM are neither necessary nor healthy for the engines. I also don't see any problem with an increase of airspeed in the descent, as long as the airspeed needle out of the yellow and red range.

With proper planning, this seems to work out fine. Some minor adjustments may need to be made for a significant headwind or tailwind.


--Randall Griffin
Good advice. I pretty much do the same thing and let the airspeed go higher (just keep it out of the yellow) during what I call "Initial Descent". Then when I get to the location and altitude that I need to transition to "Approach", I reduce MAP & RPM to 20 squared and hold altitude until she slows down to where I can drop flaps one notch. Once you get the flaps down to that first notch you can use higher MAP & RPM as required to get the airspeed you need with the descent you want. Then when I get closer to my airport I again reduce my descent rate (maybe even level out again) to bleed off more airspeed until I get to where I can lower the gear and then continue with adjusting airspeed and flaps as needed.

I think the key point is the Connie is a slippery bird and does not slow down quickly...you need to allow much transition time...even when you level out to reduce airspeed it's going to take longer than you think.

Keep experimenting and you'll find what you need to do.

Stratocruiser2
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Re: Quick descent in the connie. How????

Post by Stratocruiser2 »

Artur wrote:I think there is nothing like "quick descent", the only way is to reduce MP below prop RPM...
I know the rule that prop should not drive engine, but seems there is no other way.
As long as speed will drop to first dot, deploy flaps, and from now on things are getting better
As I understand it, the rule of "keeping everything squared" is not quite as important when you are reducing power as it is when you are increasing power where not adhering to the rule can put a lot of strain on the engine. So you can probably reduce MP below prop RPM for a short while if you want to lose speed but remember once you start increasing power again you should increase the MP first. If I am wrong however I am open to correction by those more knowledgeable than me on engine management.

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Aymi
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Re: Quick descent in the connie. How????

Post by Aymi »

It was easier with the reverses on the strat :mrgreen:

More realistically ...

What you described as a problem can be tunred into a HUGE advantage because by making a slow, early descent, this tendancy to gain lots of speed with not much altitude loss, makes you able to maintain cruise speed +20kts with half the fuel consumption because you don't need nearly as much torque when descending. Reduce RPM as much as you can to minimize drag (below 20k), and do the same with MP. Just make sure there's a runway below when your altitude reaches zero :wink:
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Re: Quick descent in the connie. How????

Post by Alan_A »

I've done well with the technique recommended by CAPFlyer, which is essentially go down, then slow down. Specifically - start descent at cruise RPM squared (anywhere in the range of 18" and 1800 to 21" and 2100, depending on your cruise settings). Let her descend fast, up to yellow line is OK. But make sure to be at your approach altitude early - say 10 miles out. Then level off, set climb RPM squared (23" and 2300). Speed will start to bleed off slowly, and you should be able to get flaps, then gear out ahead of glideslope intercept. Working for me so far - and keeps her nimble around all the jet traffic.
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Re: Quick descent in the connie. How????

Post by Mitchell - A2A »

bobsk8 wrote:I am still confused when descending in the Connie, or even slowing it down. If I am flying level at say 8,000 feet and try and slow down from cruise speed, I can lower the MP to say 18" and prop to 1800 rpm and it seems like the aircraft wants to cruise along at the same speed forever. Throw in even a very slight rate of descent, and it will actually accelerate. How on earth to you get this aircraft to slow down, and I would like some specific numbers rather than " just reduce MP and keep everything squared", which seems to accomplish very little.
The desire to get down right now usually occurs when the pilot realises that he/she is too close to the destination to do a proper cruise descent. Of course, this never happens to any of us :wink: , but as a purely fantastic hypothetical I offer the following:

Assuming that you don’t care about the engines, damage to ear drums, babies crying, etc. you can do a quick descent in the Connie at low airspeed as in any other aeroplane: slow it down to gear and flap-down airspeed at altitude by reducing power and climbing and/or turning hard (you want high alpha), when slow enough dirty her up and push over at low power. You can get down pretty quickly this way but you must be very cautious about the airspeed with both the nose and flaps down.

If you keep it at around 100 mph with the power at 15” - 2,000 rpm, gear and full flaps down you will fall from the sky in a great hurry. Of course, moderating this (higher airspeed, not such low power, gear up or down, not full flaps) will still get you down fast without doing as much harm to the engines.

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bobsk8
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Re: Quick descent in the connie. How????

Post by bobsk8 »

Tried some of the suggestions that I read on this thread, and had a much better descent and speed control tonight. Thanks for the tips.
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SISU
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Re: Quick descent in the connie. How????

Post by SISU »

My experience with the Connie so far is, that at a descent rate of 500 fpm and with a power-setting of 2300 RPM @ 23" MAP, she descends with a slower IAS than with 1800 RPM @ 18" MAP (less drag?). I mostly descent at about cruise speed. To do so, I set my preffered descend-power (2200 RPM @ 22") approximately 2 minutes before TOD, she will slow down about 20 knots IAS until TOD, and will gain back those 20 knots IAS shortly after starting the descend (but will stay at about cruise speed). I plan my descent such, that I arrive at the approach altitude about 10 NM out of the FAF. This way I'm able to slow her down to approach speed in time. To slow her down, I use a power-setting of 2300 RPM @ 23" MAP. And if she still doesn't want to slow down, I reduce MAP to a lower setting, but I always keep a positive reading on the torque-meters. Because as long as the torque meters are reading a positive value, the engines are turning the props and not vice versa. 8)
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Re: Quick descent in the connie. How????

Post by Cool »

I cruize around FL180 and I plan a TOD in NM= 3 x (alt to lose in feet/1000)

What I do is at TOD,
1/sel ALT airport to the pressu gauge and pressu rate= 400ft/mn. cowl flap at 50%
2/reduce MP to 15" and maintain RPM 2200 and stabilize descente rate around 1000ft/mn
During the descent keep monitoring MP (to maintain 15" as MP will increase with air density)
I know the copilot always ask for increasing power but no worry the 15"MP and 2200rpm is ok
This make a descent speed around 200kts more or less
3/ at approach alitude keep 15"MP and 2200rpm will reduce the speed to first white dot where it is time to set 1 notch flap when you are ready.
Do not forget to set full rpm in final to rwy.
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Re: Quick descent in the connie. How????

Post by CAPFlyer »

Cool,

Please don't operate the engine under square for extended periods of time like that. You will get wear damage to the engines like that and they will fail on you prematurely. Accusim does simulate back-loading damage, and descending under square will cause that after a short period of time.
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Aymi
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Re: Quick descent in the connie. How????

Post by Aymi »

CAPFlyer wrote:Cool,

Please don't operate the engine under square for extended periods of time like that. You will get wear damage to the engines like that and they will fail on you prematurely. Accusim does simulate back-loading damage, and descending under square will cause that after a short period of time.
What is "square" ?
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mallcott
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Re: Quick descent in the connie. How????

Post by mallcott »

Aymi wrote:
CAPFlyer wrote:Cool,

Please don't operate the engine under square for extended periods of time like that. You will get wear damage to the engines like that and they will fail on you prematurely. Accusim does simulate back-loading damage, and descending under square will cause that after a short period of time.
What is "square" ?
If you use it as a search term in the forum you will find all sorts of useful information as there are several topics on engine operation in the Connie already.
Basically `square` means 23" = 2,300 rpm, 19" = 1900 rpm and so on.
The `why` is why you need to use the search function.

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