Spiral dive

[Bushmanni]

I finally mastered the spiral dive and decided to share the knowledge here publicly for the benefit of all and not just the insiders. I have known of it and done it before but I couldn't count that as mastery. Here's the how-to for all those who want to know and also to those who don't. :)

 

First of all the point of the maneuver is to lose altitude as fast as possible while still being able to pull out of it when at the chosen altitude and with full weapons load. You could use this maneuver to escape a long range radar guided SAM or fighter while caught at high altitude. The maneuver is done by diving in a spiral that provides drag to allow steeper dive angle without too much acceleration as compared to straight dive.

 

You can screw up this maneuver and your helicopter in two ways. The first is rotor clash. You can destroy rotor blades in several ways while doing this maneuver. First way is going way too fast. I haven't tried how fast you can go but staying under about 250-330km/h (IAS) depending on your altitude has been safe for me. Second way is to let sideslip angle to grow too big which will get the chopper out of control and end up doing some violent turn at high speed that screws the rotors. Third way is using the rudder. You can use it a little bit but then that wouldn't do anything. Any useful amount of rudder will clash your rotors.

 

Second way is overspeeding power turbine and getting your engines shut down. Power turbine is directly connected to rotor and rotor over-RPM is going to trigger EEG safety mechanism and shut down the engines. You can over rev the rotor by pulling too much g while autorotating. You can reduce the risk a little by setting the free turbine governor setting to low. Your only other control over the issue is how hard you pull back the cyclic while diving and turning. Harder you pull, the more the rotor RPM will increase. At higher speed it's easier to over rev rotor by jerking back cyclic.

 

From previous issues follows that you need to control your speed, sideslip angle and rotor RPM during the dive. You can use speed readout in Shkval or the analog speed meter to monitor your IAS speed which is the meaningful one in this situation. You control speed by dive angle and pulling back on the cyclic. Dive angle is controlled by your roll rate. Higher the roll rate, steeper the dive. Rotor RPM is shown in the rotor RMP gauge(duh). Your sideslip angle is easiest to see in the nose vanes. You control sideslip by rolling the aircraft in to the slide direction hence turning sideslip angle into angle of attack.

 

The basic principle is to find such a dive angle that is as steep as possible but keeps you from accelerating too much and going overspeed while trying to keep rotor RPM at about 90-100%. Start the maneuver with a shallow turning dive and increase the roll rate and hence steepen the dive gradually until you reach a state that gives you good dive angle and speed and keeps the acceleration at bay. At high altitude you can't use as steep dive angle and high speed as at lower altitude so it's good to start slow and let the speed and dive angle increase slowly while getting lower.

 

Depending on your speed and dive angle you might need to start to level off about 500m before your chosen altitude or deck. Don't try to simply level off and pull up as that's going to put you in a major side slip and make it hard to control the aircraft. Instead start to make the dive angle more shallow and reduce speed until you are in a pretty much normal flying state.

 

And remember, no rudder.

 

The following example is an extreme version in the sense that the starting altitude is way higher than what it would be in a typical situation and the dive speed and angle is higher than what is easy to control. The point of of the example is to show the kind of results this maneuver can produce when pushed to the limits.

 

Here's a video of the maneuver.

http://forums.eagle.ru/showthread.php?t=83461

 

And here's the track of the video.

quick descent.trk

[tusler]

Cool way to loose altitude.:)

I guess I have been doing it wrong :huh:, I drop both throttles on the lower left out of auto which immediately slows the rotor to idle.

At the same time I drop the throttles I nose the bird over to a steep dive.

I have found I can go real fast down steep mountainsides this way without rotor clash or picking up to much rotor speed.:pilotfly:

[Luigi Gorgonzola]

:shocking: Quite interesting way to loose altitude... ;)

[Isegrim]

Youre hitting nearly 380 km/h in your track... you reach the same speed when simply putting forward the stick so why should somebody do a spiral....

its ok your blades are still on but you should give the shark a LITTLE BIT more collective for doing more G,s in the spiral and lose energy there for less forward speed and nearly the same diving rate.

 

:smilewink::thumbup: but almost not bad dude :D

[AlphaOneSix]

And switch the FT switch on the collective from "nominal" to "low".

[WildBillKelsoe]

Hey dude! Sounds like a cool way to fool incoming SAMs. I'll give it a go. Keep discovering!

And guys, be positive to the man!

[Isegrim]

Hey dude! Sounds like a cool way to fool incoming SAMs. I'll give it a go. Keep discovering!

And guys, be positive to the man!

 

 

AHHHMMM not really

but in lower alltitudes its helpfully against AAA fire cause

predicted position of target is moving fast and the whole time for the enemy AAA the point than is to manage to get out of range from the AAA fire while doing these spins:smilewink::thumbup:

 

And im a fully positive thinking guy:helpsmilie::megalol:

 

Also Alpha what do you mean with FT i didnt switch anything for a really long time at the collective........:huh: ahhhhhh FT Free Turbine :doh:

 

Edited December 29, 2011 by Isegrim

[Luigi Gorgonzola]

Also Alpha what do you mean with FT i didnt switch anything for a really long time at the collective........:huh:

 

FT = "Free-Turbine" switch. It tells the Governor what RPM to maintain.

 

By switching from "Nominal" to "Low" you're lowering the target RPM percentage value, if I understood correctly.

[AlphaOneSix]

In a rapid descent, your rotor rpm will "creep up" and you run the risk of overspeeding the rotor system, which can damage the main gearbox. Setting the FT switch to "low" tells the engines to manitain a slightly lower rotor rpm setting, allowing a faster descent without overspeeding the rotor system.