Va & Vno; Where do you draw the line?

[FlyDave]

I fly with a friend that has a C210 and is a CFII and retired American Airlines pilot. He comes with a lot of time in the air and experience.

He consistently tells me I should be slowing down to Va (105 -  116 KIAS depending on weight) when I hit any turbulence from light to moderate. He says a well respected mechanic backs him up on this.

I wanted to get different opinions on the subject and whether there is a belief that Mooney airframe is less susceptable to these stresses that brands C, P or B.

One thing I liked about the J was the top of the green arc (Vno) at 174 KIAS. I have flown my plane staying under this limit in light to slightly moderate turbulence. If it gets really bumpy - true moderate - I'll slow down. I have been of the mind that light to slightly moderate turbulence with not damage the airframe since it doesn't require full deflection of the control surfaces.

Va - Maneuvering Speed: Do not make full or abrupt control movements above this speed

Vno - Maximum Structural Cruising Speed: Do not exceed this speed except in smooth air, and then only with caution.

How do you manage your airplane with respect to turbulence? All thoughts welcome!

Thanks,

[67M20F]

I have had my F well past the airspeed indicator, with no problems in smooth air.....

 

but past smooth I just have one thing to say....

 

Do you feel lucky????

 

Really though you don't ever really know when the spar  could fail and that is what VA is for, think of it as this how fast would you drive a 50K car across a dirt road? Same with your mooney.

 

I for one if I hit any bumbs will slow down, it has little to do with damage but more to do with caring for the airframe..

 

I love my mooney and will do anything to help her grow even older than she is....

[DaV8or]

Quote: 67M20F

I have had my F well past the airspeed indicator, with no problems in smooth air.....

[GeorgePerry]

Quote: FlyDave

I fly with a friend that has a C210 and is a CFII and retired American Airlines pilot. He comes with a lot of time in the air and experience.

He consistently tells me I should be slowing down to Va (105 -  116 KIAS depending on weight) when I hit any turbulence from light to moderate. He says a well respected mechanic backs him up on this.

I wanted to get different opinions on the subject and whether there is a belief that Mooney airframe is less susceptable to these stresses that brands C, P or B.

One thing I liked about the J was the top of the green arc (Vno) at 174 KIAS. I have flown my plane staying under this limit in light to slightly moderate turbulence. If it gets really bumpy - true moderate - I'll slow down. I have been of the mind that light to slightly moderate turbulence with not damage the airframe since it doesn't require full deflection of the control surfaces.

Va - Maneuvering Speed: Do not make full or abrupt control movements above this speed

Vno - Maximum Structural Cruising Speed: Do not exceed this speed except in smooth air, and then only with caution.

How do you manage your airplane with respect to turbulence? All thoughts welcome!

Thanks,

[Stefanovm]

I mostly follow GeorgePerry's advice. In the past, I always slowed my Cesnna's (except 310) to Va in most all turbulence, but they rode differently. Control normally required much more control deflrection than my Mooney. The 310 was closer to my Mooney's ride and control input requirements. My wife's grip on the handhold also normally dictates when to slow down. In the Mooney, she is much more tolerant and is insistant that the ride is much better in turbulence. However, I try to stay out of the yellow arc in less than smooth air. I will go to 65%, or less, and LOP to get a seemingly smoother ride. It may only be habit and perception making me believe it is smoother. I have less than 75 Mooney hours with several cross countries from Texas to AZ and NV. The mountains and summer desert environment seem to have lots of turbulence. At 6K MSL one is not 6K agl on these cross countries, which seems to be a good rule of thumb, so it is 10K MSL+. I am limited by no on board O2.

[mikefox]

One quick note on Va.  Many pilots are sorely mistaken about the meaning of Va.  Slowing to Va simply means that the limit loads on the wing will not be reached prior to aerodynamic stall.  So you are not likely to cause structural damage to the main spar at or below Va.

However, Va does not necessarily say anything about loads on other parts of the aircraft.  There can be severe loads imposed on the tail structures, empenage, etc. from turbulence and/or control movements at speeds below Va.  All we need to look at for proof is AA587.

If one had access to all the engineering data for an aircraft, one could make more informed decisions about imposed loads, but this is not usually available to the pilot.  We should also worry about fatigue to metal parts with the loads imposed by turbulence.

In any turbulence beyond light, it is wise to slow the aircraft to Va. The lower gust loads will reduce metal fatigue issues. It gives a better ride to the passengers as well!

[FlyDave]

Thanks for the input guys - George - Great write up. I belive we're on the same page.

As I stated, one of the things that drew me to the J was to top of the green arc. My thinking was that you're probably not going to bend up the airplane hitting even moderate at 9K' - 10K' at 135 KIAS and if you need to slow down to Va you only have 20 knots to loose. Descents from those altitudes are a bit different because I keep the RPM at 2500 and the throttle at around 24" as long as I can. I start my descents around 50 miles out and at 175 knots GS, I'm really "Haulin' the frieght"!! This is just one of the things I love about my Mooney. But if I'm descending through an area known to produce turbulence (mountainous area with winds, hot deserts, etc.) I'll descent at a slower airspeed.

WRT passengers, if I just had another pilot in the plane, I would slow down later into turbulence, provided it was less than moderate. But with non-pilot passengers I'd slow down much sooner.

So, bottom line is, as George said, good judgement (which I belive I have) and I should be fine. After all, I ain't flyin' a Piper no more!!

[danb35]

Quote: DaV8or

OK, so I want to slow down in a hurry to 135 mph, but I can't just chop the power or I shock cool the engine.

[DaV8or]

Quote: danb35

Shock cooling is an OWT--don't worry about it.  Still takes a while to slow down the plane, but feel free to reduce power as required/desired.

[DaV8or]

Quote: JimR

Agreed.  Look at all of those trainers, ag, and jump planes that soldier on to TBO and beyond.  

[67M20F]

Quote: DaV8or

Are you saying you have flown your Mooney beyond VNE?? If so, that is brave.

My question on this subject is how do you slow down in time? This happened to me on the last flight I took. I was on decent into Oakland and out of nowhere I hit moderate turbulance. I really wasn't expecting it, it wasn't that kind of day. It was bad enough that I hit my head on the roof. The Fed EX guys in Caravans were bitching about it too.

OK, so I want to slow down in a hurry to 135 mph, but I can't just chop the power or I shock cool the engine. I was trying to decend into Oakland and get under a cloud layer, so I really didn't want to gain any altitude. Going way to fast for the gear and I don't have speed brakes. So I pulled the throttle a bit faster than usual, went to a low RPM, continued the decent, tightened my seatbelt and rode it out. Made me really consider again the speed brakes!

[Jeff_S]

There is a very well-known technique for reducing airspeed quickly that requires neither gear down nor speed brakes. People just don't practice it and unless you've done any formation flying it probably never occurred to you.

Side slip.

If you need to cut speed quickly and maintain altitude, just throw in a little side slip and that fuselage acts like a nice big airbrake. I learned this while practicing formation flight for a Cessnas to AirVenture arrival (I was in a Warrior, and ended up not being able to participate, but those are different stories!) and it's a nice way to bleed off a few knots, keep your spot in the air, etc.

Might help if you're worried about shock cooling. As to trainers making TBO, I do think that's more the norm than the exception, but I also think it's because they get flown a lot. As Mike Busch and most other A/Ps will say, the bigger problem in the GA fleet is corrosion from lack of flying time, not people blowing out their engine through abuse.

[jlunseth]

I fly a 231 so I just have one question.  What turbulence?  Oh, maybe you mean during the descent? Slow your descent speed a little.

[Hank]

I've only slowed for turbulence one time. There was an airmet for moderate turbulence from pretty much the Miss. River and west. Left Rapid City headed to Cody, WY, nice and smooth at 8500, airmet or no. Approaching the Philipi VOR, it got bumpier than I was comfortable with [departing near gross, with the wife, loaded for vacation] and I slowed down to Va. Haven't needed to since.

To descend, I typically pull the throttle back two inches and trim for 500 fpm. Walk the throttle back and mixture forward as air pressure rises, to keep the initial descent throttle setting and cruise EGT. With my carb, LOP just doesn't work. Airspeed typically climbs to around 160 mph indicated, sometimes higher, vs. Vno = 175 mph, Va = 132 mph or less. 160 indicated at 10,000 msl = 192 mph, quite respectable for a 40-year-old plane running a 60-year-old engine design. In the summer, it can get bumpy coming down, but speed usually bleeds down in the thicker air, too, and by 4000 msl I rarely indicate even 150. Maybe my 3-blade works as an airbrake to some extent; I use it that way on purpose sometimes, too.

[DaV8or]

Quote: JimR

That's interesting, Dave.  I'm sorry to hear it.  Hopefully they were all rentals!   

I'm all for taking it easy on the old girls.  I changed my oil today and it occurred to me that my Mooney is 32 years old and has over 10,000 hours on her.  She's earned a little pampering.   

As for shock cooling, I guess then that the only solution for you is to either buy those speed brakes that you mentioned or begin your descents sooner.  Speed brakes have always just seemed like a terrible waste of energy to me.  But I don't typically fly in the complex airspace that some of you guys do that necesitates them. 

Jim 

[DaV8or]

Quote: Jeff_S

There is a very well-known technique for reducing airspeed quickly that requires neither gear down nor speed brakes. People just don't practice it and unless you've done any formation flying it probably never occurred to you.

Side slip.

[DaV8or]

Quote: 67M20F

 

[GXPD]

If you have a 3-blade prop (no limitations on RPM other than extended ops <15"mp) you can slow down  by reducing MP to 17-18" and reduce rpm to 1900.  Once at 120mph, drop gear and bring prop back to normal and MP as required.  Works for me.  Prop acts as a large disc brake

[flight2000]

Quote: GXPD

If you have a 3-blade prop (no limitations on RPM other than extended ops <15"mp) you can slow down  by reducing MP to 17-18" and reduce rpm to 1900.  Once at 120mph, drop gear and bring prop back to normal and MP as required.  Works for me.  Prop acts as a large disc brake