Chinook IRL hover attitude question

[MagicSlave]

What is the hover attitude of our Chinook in real life (and our simulated Chinook once we get DAFCS, DASH, LCT and other bells and whistles)? Pitch level or some degrees nose up? If level, how do the Chinook pilots execute pinnacle style rear wheels only landing from hover?

 

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[cw4ogden]

@MagicSlave

Upon liftoff the LCTs retract to facilitate a level fuselage hover.  This is primarily for the triple point cargo hook system, as all hooks need to be level for ground crews to hookup.  
For a two-wheel "ridgeline" type landing, after landing, the pilot can apply aft cyclic up to two inches, to force the LCTs to "ground" or may place the LCTs in manual to prevent them cycling between ground and retract.  

There was an accident in Afghanistan around 2006, where cycling LCTs during a ridgeline landing likely caused the aircraft to liftoff and drift forward.  On their second attempt to pickup troops, they had a blade strike on the aft head.  A second attempt they would not have needed if placing the LCTs in manual was required.  It is, or was back then at least, purely pilot preference.  They attempted to fly to a safe landing spot but lost the aft rotor system about 30 seconds later.  

Edited September 12, 2024 by cw4ogden

[MagicSlave]

@MagicSlave
Upon liftoff the LCTs retract to facilitate a level fuselage hover.  This is primarily for the triple point cargo hook system, as all hooks need to be level for ground crews to hookup.  
For a two-wheel "ridgeline" type landing, after landing, the pilot can apply aft cyclic up to two inches, to force the LCTs to "ground" or may place the LCTs in manual to prevent them cycling between ground and retract.  

There was an accident in Afghanistan around 2006, where cycling LCTs during a ridgeline landing likely caused the aircraft to liftoff and drift forward.  On their second attempt to pickup troops, they had a blade strike on the aft head.  A second attempt they would not have needed if placing the LCTs in manual was required.  It is, or was back then at least, purely pilot preference.  They attempted to fly to a safe landing spot but lost the aft rotor system about 30 seconds later.  

Thank you for the insight. So, with weight on rear wheels OR LCTs manually retracted the natural stable hover attitude would be a little nose high, while weight off wheels and LCTs in AUTO is level fuselage hover?

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[cw4ogden]

@MagicSlave

 

 

Correct.  When the LCTs drive to ground, the rotor heads tip forward like a traditional helo putting forward cyclic in.  This helps with 4 wheel taxi, to give some inherent forward thrust while taxiing.  So in the two wheel landing scenario, with LCTs in auto, you can anticipate needing a bit of aft cyclic to maintain the same pitch attitude, when they drive to ground.  Often times in auto the LCT will cycle between ground and retract, even with 2 inches of aft cyclic, in which case you can pitch the nose up just by adding a touch of thrust (collective), as your back wheels are a pivot point. 

I highly recommended to trainees to use manual, mainly because of that accident.  The only drawback to placing them in manual is the possibility the crew might forget upon departure, reach a fast cruise speed, unwittingly placing serious stresses to the rotor system.

It's a maneuver that looks tricky, but really isn't all that difficult unless your cockpit is overhanging a huge drop off.  We get lots of practice hovering with the Nonrated crewmembers giving us directions, so it's no more difficult than a sling load hookup or precision hovering task.  It's actually easier once the back two wheels are firmly planted. 

The craziest one I ever did was in Korea where we sat on a maybe 15 meter clearing high up near the peak of a small mountain.  The Koreans had saws and yard tools to de-vegetate an unmanned mountain EW outpost.  So a tree covered mountain where they had lopped off just enough trees to get the back of a chinook in.  I think we were there a good 10 to 15 minutes while they unloaded.   Edited September 13, 2024 by cw4ogden

[adrift_foolish1]

No. Lct's in auto at a hover (fully retracted) is about 5 degrees nose high. The further the lct's are manually programmed forward the more the nose must be raised to maintain a hover.

[Hot_LZ]

@MagicSlave @cw4ogden

A couple things stated here are actually incorrect. @adrift_foolish1 is correct. To be very anal about it, I'd say the hover attitude is about 4 degrees nose up. It is absolutely not level. Also, after landing the SOP is to apply 1.5 inches aft cyclic. And you can use up to 3.5 inches aft cyclic to plant the aft gear into the ground. I believe the 2 inches you mention are from earlier Chinook models (C and older). Ofcourse you could try to apply more, but then you're likely to encounter droop stop pounding.

Also, the LCT's do help with forward taxiing, but they're not necessary as even without LCT's the Chinook would taxi forward. This is because of how the rotor system is rigged. The forward mast is angled 9 degrees forward, the aft mast is angled 4 degrees forward.

In a two wheel landing situation, or the so-called ridgeline landing, you would apply 3.5 inches cyclic aft to plant the aft gear firmly onto the ground, then use thrust only to maintain attitude. The use of LCT's in manual at this point is a technique, but is not really necessary in most circumstances. Unless you're unstable for whatever reason.

[MicroShket]

I am sorry for being uneducated, but I would be glad to know the stroke of the cyclic in both directions in inches. 

Thanks. 

[Hot_LZ]

I don't think anyone here would know the answer to your question, that's a very hard one . You would have to get in the cockpit, get hydraulic power on it and measure. But it'd hard to measure because there's no clear centerpoint.

[cw4ogden]

On 1/19/2025 at 9:17 PM, MicroShket said:

I am sorry for being uneducated, but I would be glad to know the stroke of the cyclic in both directions in inches. 

Thanks. 

It's roughly 8 inches forward and 5 inches back per the limits of the D model stick position indicator.  

[MicroShket]

28 минут назад, cw4ogden сказал:

8 inches forward and 5 inches back

Thank you, sir! I appreciate your help. Because everywhere I see "move stick 1.5 inches back", etc. But I couldn't determine the scale for gaming devices without knowing your information. 

Edited January 22 by MicroShket

[MagicSlave]

Thank you, sir! I appreciate your help. Because everywhere I see "move stick 1.5 inches back", etc. But I couldn't determine the scale for gaming devices without knowing your information. 

There is the longitudinal stick position indicator scale for that in the front panel, pilot's side

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