Practical Hydroplanning Advice

[aviationluver]

I just realized something the other day. I know the types of hydroplanning and formulas. However, no one has really taught me practical techniques to use while facing hydroplanning in real-life during Takeoff and Landing.

The only advice I have ever received was that while facing hydroplanning during landing, you would want to plant the aircraft firmly on the ground. No advice about use of thrust reverse.

The are three types of hydroplanning. Dynamic, viscous and reverted rubber. There are two scenarios that we can encounter. Take off and landing. So, that should mean that there should be 6 scenarios we can face. So, what techniques would you use in these 6 scenarios?

Look forward to your responses :D

[421dog]

ok, just 'cause it's low hanging fruit...

I'm glad you're "..planning" about hydroPLANING".

Sorry, just couldn't resist. I'm sure someone here has something relevant to say.

[Intruder]

Techniques will vary with the type of airplane (light/heavy), installed equipment (antiskid brakes, thrust reversers, etc), and Operating Manual procedures. Also, there is no way for you to analyze and identify the type of hydroplaning you might encounter in real time.

On takeoff, hydroplaning should not be a factor except in a significant crosswind. Use normal crosswind techniques. If you think controlability will be a problem, don't take off!

On landing, there may be 2 significant factors that affect hydroplaning: crosswind and braking. Again, use standard crosswind techniques when applicable. Use the longest runway available and use charts for "poor" braking conditions if you think hydroplaning will be a problem. If landing distance is marginal, go somewhere else. If you encounter controllability problems on the runway due to hydroplaning, consider a rejected landing.

Use aerodynamic braking if allowed. If you have thrust reversers, use them to minimize wheel braking. If you have anti-skid brakes, use them, because they will work to minimize the effects of hydroplaning. If no anti-skid brakes, use them judiciously and release them if you start skidding.

[singpilot]

A couple of additionals.

Fly the airplane down the runway...meaning those flight controls still put out a lot of effort even though all three gear are on the ground.

Discontinue all reverse thrust IMMEDIATELY if yaw is anything other than down the runway. The reversers will suck you sideways if a skid starts. Once straightened out again, you can go back to them, but beware the sideways yaw in T/R.

AntiSkid is your best friend.

[Milt]

There is that rough old formula for determining the hydroplaning speed of a pneumatically tyred vehicle, be it a bicycle or an A380.

Speed in MPH = 9 X (the square root of the tyre pressure in PSI).

That means that you will lose it in your car, having tyre pressures of 36 PSI, at any speed over 54 MPH when you try to traverse across sheet water on the road.

There is no function for weight so planting your aircraft hard on to a water covered runway or smooth lake at speeds above the hydroplaning speed will not get your tyres through a water layer. Give this myth to the Mythbusters.

Regardless I don't want to be the first to skim a lake with a heavy heavy.

[Agaricus bisporus]

A Hydroplane is a kind of speedboat. Did you by any chance mean to ask about "Aquaplaning"????

Hydroplane - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/Hydroplane)

Never mind. Accuracy has never been seen as particurlarly important on PPRuNe.

[Checkboard]

you would want to plant the aircraft firmly on the ground.
This advice is in the Boeing manuals in order to encourage you not to waste runway. The aircraft slows down much faster on the runway than floating above it - so aquaplaning conditions are not the time to stretch the hold-off attempting a "greaser". Having said that, as stated above, a soft or firm touchdown has no effect on any subsequent aquaplaning.

Speed in MPH = 9 X (the square root of the tyre pressure in PSI).
This formula is only relevant if the depth of the water (above the highest points of the surface) exceeds the depth of the tyre tread. You really only need be concerned for flooded runways - this is why 3mm water depth figures in the charts so much. It is worth noting your tread depth visually on the walkaround, if you are operating in wet conditions. It is also why you nay have landed on many wet runways, but never experienced the sudden loss of friction from aquaplaning.

This is also why grooved runways are so effective - water sitting in the grooves doesn't count, and braking on a wet grooved runway is considered by Boeing as equivalent to that on a dry runway. (As an aside, "chevron cuts" - the V-shaped cuts you see on tyres are caused by overly-heavy braking on a grooved runway.)

In 12,000 hours, I have only aquaplaned twice, both times in jets, both times landing in tropical downpours on flooded runways. The experience is much like landing a taildragger - in that, as above, you must constantly "fly" the aircraft by staying lively on the controls (ailerons into wind, rudder to keep straight) until the speed drops (which happens veeerrrryy slowly :eek:) below the aquaplaning speed and the brakes become effective. The aircraft skitters about just like driving on ice at high speed :eek:.

It is also important that your crosswind landing technique is good enough that you are certain you will touch down with the aircraft tracking down the runway centreline - any drift on touchdown on a flooded runway will probably see you off into the bushes. :oh:

[RMC]

Lots of HP incidents result from crews not spotting contaminated conditions early enough (sudden heavy downpour after preceeding has landed...but before runway inspection takes place). Practical tip ....if your windscreen wipers are on high and still not clearing ...smell a rat.

[ahramin]

A Hydroplane is a kind of speedboat. Did you by any chance mean to ask about "Aquaplaning"????

Hydroplane - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/Hydroplane)

Never mind. Accuracy has never been seen as particurlarly important on PPRuNe. Amazing the new class of "intellectuals" we are getting out there who think an entry in a free encyclopedia, written by anyone who feels like it, is a supporting argument.

Agaricus bisporus, may I recommend something less flavour of the day but more practical in terms of not looking like an idiot: a dictionary. My copy of the Oxford English Dictionary contains the following entry:

hydroplane
noun 1 a light, fast motor boat. 2 a fin-like attachment which enables a moving submarine to rise or fall in the water. 3 us a seaplane
verb another term for aquaplaneWhile I am sure you are far more accurate than the rest of the PPruners here, perhaps one of them might enlighten you on the difference between a noun and a verb.

[Checkboard]

Most people are familiar with the 9*square root formula from D. P.Davies excellent "Handling the big jets", however, if you want to read the original NASA research paper, gathering together and fully explaining the research from both NASA and the Royal Aircraft Establishment, it's here:

PHENOMENA OF PNEUMATIC TIRE HYDROPLANING (http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19640000612_1964000612.pdf) (1963)
By Walter B. Horne and Robert C. Dreher

You can skip the maths, but the rest is an excellent easy to understand description of the entire event, under each of the controlling conditions. :ok:

[BOAC]

2 caveats to posts above:

1) If you encounter controllability problems on the runway due to hydroplaning, consider a rejected landing. - remember that once the reversers have deployed (which should be quickly!) a 'rejected landing' is not a good idea and is forbidden in most operations.
2) As you all reach for your calculators and tech notes, remember that 9 root p is only valid for PSI in the tyre and knots on the ASI

[Intruder]

Yes. However, the OP didn't specify the airplane, so that may be an option in some cases (e.g., light airplanes, turboprops, jets sans reversers).

[BOAC]

Yer right, of course! Just thought it worth re-iterating. I also suspect the OP has been eating 'Ace the pilot interview':eek:

[green granite]

For Info
There were a series of trials done by Cranfield on aquaplaning
using a Hunter (there was a gap left between the ponds for the nose wheel to run in so the pilot had a steering function) so there should be a report on them somewhere.

[BOAC]

If anyone is searching I'm pretty sure it was a 'down-and-welded' Supermarine Swift they used for the trials.

[mustpost]

http://www.pprune.org/archive/index.php/t-253577.html

[muduckace]

Reverse thrust aside (that may disrupt water level tension). Just like a car ,the first wheel that is in the breaked position will become the pivitol point of contact. Anti skid is great.

Landing distance being degraded, the goal is to break the water tension. There are several methods to do so.

[PantLoad]

Only my opinion.....take it for what it's worth. Feel free to throw rocks at me. I won't get upset, nor will I respond.

Fundamentally, there are three kinds of hydroplaning (as mentioned). The formula mentioned is also valid, but misleading.

The 9 times the square root thing applies to a tire that is already spinning at the correct speed. If the tire is stopped (as just prior to landing), and you make a really nice touchdown, the tire may never reach the proper speed, and, at that point, hydroplaning can occur at speeds as low as 6 to 7 times the square root. Firm touchdowns will get the wheels spinning at the proper speeds.

The above formula applies only to "Dynamic" hydroplaning.

Reverted rubber hydroplaning occurs when the tire is allowed to skid. Steam (from boiling water) develops and changes the surface characteristics of the rubber. This new surface characteristic doesn't do as well in stopping the aircraft.

Finally, there is viscous hydroplaning. It occurs when there are contaminants on the runway, such as oil, fuel, rubber deposits, etc.

It is important for you to touchdown firmly at the proper speed and the proper point on the runway. Use maximum reverse thrust immediatley upon touchdown. It is also important to touch down with no lateral drift AND with the aircraft aligned with the runway. No crab. (In some cases, some aircraft, some circumstances, it is necessary to land with some crab, I know....)

If you begin to drift toward the downwind side of the runway, steering to get back to centerline is proper, but, with maximum reverse, you will drift even more. This is because the thrust vector has a lateral component when the aircraft is not perfectly aligned with the runway. So, steer to get back on centerline, and, at the same time, go into idle reverse. Once you're back on centerline and aligned with the centerline, go back to maximum reverse.

The new anti-skid systems are great. The older generation ones are not. You don't want to skid....that's the idea. If you do, you get into a reverted rubber problem. (And, possibly a control problem.)

It's quite possible to experience all three types of hydroplaning in the same landing. First, you make a really nice, smooth landing....the tire really never makes good, solid contact with the runway (dynamic). Then, you skid, for one or many of a number of reasons, and you get reverted rubber. Then, as the other end of the runway comes up, you get into a viscous hydroplaning problem....all the rubber build up from the landings coming the opposite direction...take offs in the opposite direction (oil, fuel, exhaust, etc.).....

Be aware that with reverted rubber...and most especially viscous hydroplaning, hydroplaning can and does occur at any speed...even as low as ten knots. And, many aircraft anti-skid systems do not function at slow speeds. So, this makes things worse.

Again, the idea is to use reverse thrust at max and as soon as possible after touchdown. You want to take advantage of this, as best you can, so the brakes and tires don't have to do as much work at these high speeds. As the speed decreases and reverse thrust effectiveness diminishes, the brakes, tires, and anti-skid system will have to do more of the work...which is OK, since, ostensibly, you're going slower....less chance of dynamic hydroplaning.

Follow SOP with regard to reverse thrust use....but, keep in mind, if you need it, use it. If the end of the runway is rapidly approaching, and your deceleration is not so good...use max reverse...to a full stop if necessary. While this may not comply with SOP, it's far more desirable to the alternative.

By the way, unless your aircraft tires have fancy tread designs (as automobiles have), the tread on your tires has little effect on dynamic hydroplaning. Proper inflation pressure is the critical factor. And, runway grooving is critical, as well.

As I re-read this for typos, I noticed I failed to mention the importance of getting the speed brakes out immediately upon touchdown, as well. The reason for this should be obvious.

Your company's SOP is a good benchmark for operation in adverse weather. Use of autobrake (Today's systems are great!) is desirable. Typically, autobrake, coupled with a good anti-skid system, will allow you to get maximum deceleration (for the conditions given to you), minimizing skidding, maximizing control. Again, follow your company's SOP.

Many times, under adverse conditions, you'll exit the runway at the end or a turn off near the end, where contaminants can be heavy. And, with ATC constraints, you'll be asked to 'expedite' to the next available turn off. Be careful with this, as you'll find that when it's time to slow for the turn off, you'll be unable to slow....anti-skid system is not active because of the low speed (20 Kts for the Bus)....a lot of rubber and oil, etc., on the runway....and you'll slide right past your turn off. (If you were planing to expedite to the last turn off, you'll have problems....obviously.) So, resist the 'go along, get along' with ATC. They know (or should know) to give a bit more spacing on aircraft on approach, as it'll take a bit longer for aircraft to decelerate and clear the runway under adverse conditions. If the aircraft behind you has to go around, it won't be your fault....it'll be ATC's fault. In other words...one of flying's golden rules: Don't let ATC fly your aircraft!

Just my two cents...


Fly safe,


PantLoad

[green granite]

If anyone is searching I'm pretty sure it was a 'down-and-welded' Supermarine Swift they used for the trials.The Swift was replaced by the Hunter.

From flight archive: 1971 | 1620 | Flight Archive (http://www.flightglobal.com/pdfarchive/view/1971/1971%20-%201620.html)
However, the department also undertakes research
and development flying under contract to the Ministry of
Aviation Supply, and recent projects have included
aquaplaning trials using a Hunter and variable stability
research for which a Bassett and, more recently, a Twin
Comanche have been the vehicles.

Also mentioned in this blog:http://viewfromthecockpit.*************/2009_07_01_archive.html

The Department of Flight, which operated the Doves, also had a French Morane-Saulnier MS 760 Paris jet for flight testing. The department also operated a Supermarine Swift jet fighter (later replaced by a Hawker Hunter) for aquaplaning trials carried out on the main runway. To facilitate these trials the runway was checker-boarded with rubber dams which formed artificial lakes. Cranfield also had a gliding club and in addition the Department of Flight operated a Training Flight using Auster Aiglets. This was my idea of heaven.

In place of the *** use

b l o g s p o t/2009_07_01_archive.html (without the spaces)

[Centaurus]

The Boeing FCTM makes an interesting point about releasing the brakes if you are going sideways in reverse during the landing run on a slippery runway with crosswind. Among other things it states: "To correct back to the centreline, reduce thrust to idle reverse and release the brakes". It also says "Main gear tire cornering forces available to counteract this drift are at a minimum when the antiskid system is operating at maximum effectiveness for the existing conditions."

So you have the situation where a slippery runway has a crosswind and normally the pilot would select an appropriate autobrake setting depending on landing weight and runway length. You plant the aircraft beautifully at the 1000 ft markers and apply full reverse (reverse is most effective at high speed) and you think the autobrakes are working but it is initially hard to tell on a slippery runway. They are probably working but the decelleration is hard to feel although you could have a quick glance at the green line going backwards on your glass cocpit ADI.

A sideways drift hits and the aircraft weathercocks. The book says to go to idle thrust (ever tried to reduce to idle thrust quickly without coming out of reverse completely - you need lots of practice I tell you).

The N1 is spooling down and you quickly dab hard on the downwind brake in order to straighten up. That dab immediately disconnects the autobrake system and the aautobrake disarm light comes on. Chances are the PNF does not notice the autobrake light illuminate because he is sweating on you straightening the aircraft before it slides off the edge. You didn't see the light come on either, because you too are sweating on trying to straighten up.

The aircraft now is hopefully straightening up under the influence of your dab of the downwind brake pedal and you relax knowing the autobrake is working hard to pull you up - except it has been inadvertently disengaged by your little dab. Now tracking straight you rip back into reverse but it takes a long time from 23 percent N1 in idle reverse to wind up to 89 percent or full reverse. No problem with a long slippery runway but a real bind if it is a limiting length runway.

Let's go back to the advice contained in the FCTM. How would you interpret that advice with regards to the words "Reduce reverse thrust to reverse idle and release the brakes."

Does this mean you switch off the autobrakes? If so, what is the fastest way of doing that? Override by depressing hard on the brake pedals - or maybe having the PNF turn the autobrake selector off? Or perhaps put the speed brake lever in the down detent which turns off the autobrakes? The latter is a bit of a risk because you need spoilers to dump lift and put weight on the mains.

It all becomes a bit convoluted doesn't it. The tricky part as I see it is deciding in a flash how to take the brakes off as you are going sideways. Makes for a good discussion.

[Iceman49]

Landed on a runway after a rainfall, this particular base rarely experienced rain. As soon as the reversers were deployed we were traveling sideways down the runway. There was nothing in our training to account for this unusual manuver...when in doubt reverse what you had previously done. Reversers were stowed, aircraft recentered...don't remember what I did with the brakes. Tower asked if we were ok...said I needed a clean flight suit.

[bayete]

Maybe you should ask these guys about hydroplaning.
YouTube - The Runway is Wet (http://www.youtube.com/watch?v=VWovoK4Ja_8)

[Intruder]

Landed on a runway after a rainfall, this particular base rarely experienced rain. As soon as the reversers were deployed we were traveling sideways down the runway. There was nothing in our training to account for this unusual manuver...
Our Flight Handbook addresses the issue in the "Wet/Slippery Runway Landings" section. Initial training includes discussion and pictures with appropriate vector diagrams.

The reverse thrust side force and a crosswind can cause the aircraft to drift to the downwind side of the runway if the aircraft is allowed to weathervane into the wind. As the aircraft starts to weathervane into the wind, the reverse thrust side force component adds to the crosswind component and drifts the aircraft to the downwind side of the runway. Main gear tire cornering forces available to counteract this drift will be reduced when the anti-skid system is operating at the maximum braking effectiveness for existing conditions.

To correct back to the centerline, reduce reverse thrust to reverse idle and release the brakes. This will minimize the reverse thrust side force component without the requirement to go through a full reverser actuating cycle, and provide the total tire cornering forces for realignment with the runway centerline. Use rudder, steering and differential braking as required to prevent overcorrecting past the runway centerline. When re-established on the runway centerline, reapply steady brakes and reverse thrust as required to stop the aircraft.

[Iceman49]

Military 1975

[jcbmack]

And no, the FAA does not specify much on reverse thrust.

[OverRun]

The website is not co-operating for the link to:
PHENOMENA OF PNEUMATIC TIRE HYDROPLANING (1963) By Walter B. Horne and Robert C. Dreher

I shall keep trying, but a slightly later paper by Tom Yager of NASA on FACTORS INFLUENCING AIRCRAFT GROUND HANDLING PERFORMANCE is here (http://www.geocities.com/profemery/yager.pdf). It's a good read.

[Checkboard]

It's a PDF file-here is the actual address:

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19640000612_1964000612.pdf

[Microburst2002]

Yes indeed
If there is a change in the next revision it means they have spies watching PPRUNE
And Boeing pilots will owe it to you!

Cheers

[Pugilistic Animus]

What is the maximum allowable tire pressure differential allowed for part 119 operators?...can you yourself just check with a gauge:E?

[Ocampo]

Reading this topic something immediately came up to my mind.
One landing from a 4 hour flight on a Piper Cherokee, heavy rain shower just 15 before landing, even the low-level CB's were still there when we were on finals. Tried to plant it (turned out to be no so "planted"), and right away, after nose gear touchdown the tail starts to swerve(?) erratically left to right (like the racing motorcycle's tail when the bloke is about to be thrown to the floor). Immediate reaction, elevator nose down, don't touch the brakes and let the airplane decelerate by friction. The "scare" came up just after the turn-off.
I guess it happens to the little ones as the big ones also...who would've thought? :rolleyes:

[jcbmack]

What is the maximum allowable tire pressure differential allowed for part 119 operators?...can you yourself just check with a gaugehttp://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/smilies/evil.gif

Tire pressure should be checked atleast 2 hours after the last operation with a gauge at ambient temperature. A temperature-sensing valve in each tire can release air pressure on aircraft as well.

I found relevant info on tire pressure differentials in FAR 21, 23, and 25.

I look forward to hearing a more thorough response from anyone who knows.

p.s. even with Nitrogen filled tires there will be temp dependent pressure changes that can be modified by a sensing system.

[Pugilistic Animus]

by the pilot??? and for differential answer= 60/40

[jcbmack]

FAR 121 too. Those who are certified to check the tire pressure.

[Pugilistic Animus]

Does not checking the pressure release the nitrogen and lower the pressure?

all part 119 carriers

[jcbmack]

Does not checking the pressure release the nitrogen and lower the pressure?

Yes indeed; I should have not missed that.

All 119 carriers; all who are certified.

Thank you PA.

[Pugilistic Animus]

maintenance personnel/ mechanics/ engineers

[jcbmack]

...and for differential answer= 60/40

Recent SAFO... yeah pressure would go down from checking the pressure. :{

[Pugilistic Animus]

for a plotted true course of 090 I find that before correcting for the wind I have to fly a magnetic course of 087 finally with a WCA of 8E giving me a CH of 079 what is my VFR cruising altitude
a. above 3000' agl
b. above FL 180
c. below 1500' agl

[jcbmack]

for a plotted true course of 090 I find that before correcting for the wind I have to fly a magnetic course of 087 finally with a WCA of 8E giving me a CH of 079 what is my VFR cruising altitude
a. above 3000' agl
b. above FL 180
c. below 1500' agl


I choose a more than 3000' agl due to the magnetic course; prior to correcting for wind, the altitude above ground must be atleast 3000' VFR cruising.
MC= true course plus or minus variation. MC between 0 and 179 degrees at odd altitudes MSL plus 500 feet. MC determines odd or even altitudes.IFR traffic could be 500 feet above or below. Staying straight and level is imperative; do not go wandering into other's airspace.
See and avoid, or see and be seen... at higher altitudes aircraft fly faster, thus proper VFR cruising agl is critical. Of course there exceptions for level flight, but these are NOT covered under VFR cruising altitude.
These are: 1000', 1500', 2000', and 2500'. There will be increased traffic below 3000'.

[jcbmack]

For a synopsis see: Federal Aviation Regulation Sec. 91.159 - VFR cruising altitude or flight level. (http://www.risingup.com/fars/info/part91-159-FAR.shtml)

[muduckace]

Not to any significant measure, probably more licks in a tootsy pop to get to the center than checking tire pressure to lower it more than 1 psi.

[Pugilistic Animus]

:confused::confused::confused:
so 1500' feet require use of the semicircular rule; I can fly VFR at FL180?
and
no one noticed that I wrote E instead of L for the WCA?

and

that's why pilots don't fiddle with high pressure tires:rolleyes:

[jcbmack]

VFR cruising alt. is at 3000'. Below 3000' it is no longer called VFR cruising altitude, so my answer is still correct.:suspect:

[jcbmack]

Not to any significant measure, probably more licks in a tootsy pop to get to the center than checking tire pressure to lower it more than 1 psi.


Nitrogen gas, a group 15 element, with a valence shell rangin from 1-5; being a relatively inert gas due to its electron configuration and readiness to form double bonds. It still will expand and contract due to temperature, and even with a 1 psi reduction in pressure, there will be some significant less potential for pressure going over the limits.
Nowadays some aircraft are equipped with sensing systems in each tire that can relieve tire pressure as needed due to changing temperature conditions.

[jcbmack]

I can fly VFR at FL180?


No, as it is class A controlled airspace. It is IFR for FL180 to FL 600 (18000'-60000') Jet routes are included in class A airspace.

However, if you lose all two way radio communications in VFR clearance.
Read the AIM:

6-4-1. Two-way Radio Communications Failure

... 2. VFR conditions. If the failure occurs in VFR conditions, or if VFR conditions are encountered after the failure, each pilot shall continue the flight under VFR and land as soon as practicable.
NOTE- This procedure also applies when two-way radio failure occurs while operating in Class A airspace. The primary objective of this provision in 14 CFR Section 91.185 is to preclude extended IFR operation by these aircraft within the ATC system. Pilots should recognize that operation under these conditions may unnecessarily as well as adversely affect other users of the airspace, since ATC may be required to reroute or delay other users in order to protect the failure aircraft. However, it is not intended that the requirement to land as soon as practicable" be construed to mean "as soon as possible. Pilots retain the prerogative of exercising their best judgment and are not required to land at an unauthorized airport, at an airport unsuitable for the type of aircraft flown, or to land only minutes short of their intended destination.


FAR 91.185
91.185 IFR operations: Two-way radio communications failure.
(a) General. Unless otherwise authorized by ATC, each pilot who has two-way radio communications failure when operating under IFR shall comply with the rules of this section.
(b) VFR conditions. If the failure occurs in VFR conditions, or if VFR conditions are encountered after the failure, each pilot shall continue the flight under VFR and land as soon as practicable.


FAR 91.59

Sec. 91.159 VFR cruising altitude or flight level.

Except while holding in a holding pattern of 2 minutes or less, or while turning, each person operating an aircraft under VFR in level cruising flight more than 3,000 feet above the surface shall maintain the appropriate altitude or flight level prescribed below, unless otherwise authorized by ATC: (a) When operating below 18,000 feet MSL and—
(1) On a magnetic course of zero degrees through 179 degrees, any odd thousand foot MSL altitude +500 feet (such as 3,500, 5,500, or 7,500); or
(2) On a magnetic course of 180 degrees through 359 degrees, any even thousand foot MSL altitude +500 feet (such as 4,500, 6,500, or 8,500).
(b) When operating above 18,000 feet MSL to flight level 290 (inclusive) and—
(1) On a magnetic course of zero degrees through 179 degrees, any odd flight level +500 feet (such as 195, 215, or 235); or
(2) On a magnetic course of 180 degrees through 359 degrees, any even flight level +500 feet (such as 185, 205, or 225).
(c) When operating above flight level 290 and—
(1) On a magnetic course of zero degrees through 179 degrees, any flight level, at 4,000-foot intervals, beginning at and including flight level 300 (such as flight level 300, 340, or 380); or
(2) On a magnetic course of 180 degrees through 359 degrees, any flight level, at 4,000-foot intervals, beginning at and including flight level 320 (such as flight level 320, 360, or 400).


So, yes under zero radio communication you may fly VFR in FL180. VFR cruising altitude is 3000' or better except under brief circumstances.

[jcbmack]

A Hydroplane is a kind of speedboat. Did you by any chance mean to ask about "Aquaplaning"????

Hydroplane - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/Hydroplane)

Never mind. Accuracy has never been seen as particurlarly important on PPRuNe.

No!!! And wikipedia is not a legitimate resource anyways. Hydoplaning does refer to a speedboat at the surface of water; water has higher surface tension due to its hydrogen bonds and air water surface interface. The official term used for the "aquaplaning" of tires with water on a run way is also called hydroplaning. There are 3 types of hydoplaning which are as follows: dynamic, viscous and reverted rubber. Dynamic hydroplaning requires 0.1 of an inch or more of standing water onm the runway. Any of the following can worsen the hydroplaning issue: excessive tire wear tread, lack of depth groove, and tire, overinflation. In the airplane itself it feels like sliding and jerking, usually from side to side.
Viscous hydoplaning is believed to be the most common of the three types of hydroplaning. Viscous hydroplaning occurs on smooth runways or ones where there are rubber deposits, like in the touch down area.
Reverted rubber hydpoplaning require a wet runway and a skid in progress. This is due to brake lock and the heat produced by friction. In physics this is termed a form of balancing force. The heat is energy in transit due to temperature difference produced by the excitation of molecules by the force of friction.
The formula to determine the speed of an aircraft when hydroplaning is 8.6* the square root of the tire pressure measured in IB/in^2 (pounds per square inch) This equation gives you the lowest entry speed. However, the nosewheel and the main gear will begin hydroplaning at a different speed in knots. The best way to avoid hydoplaning is to touch down below the minimum recommended touchdown speeds if there is water on the runway. Once hydroplaning begins, it can continue below the minimum hydroplaning speeds.

Pilot's Encyclopedia of Aeronautical Knowledge is your friend:ok: while wikipedia is not:eek:...
Contaminated tires can be an often overlooked, but important issue.

[Sir George Cayley]

3mm of water. Below that figure the runway is wet. Deeper water means it's contaminated. Greater than 13mm er something else terrible happens.

If you call finals and tower tell you recent rain, wet with water patches would it be so bad to loitter for a few more mins until wet appears on the ATIS?

Sir George Cayley

[jcbmack]

3.0mm= O.118 inches with three digits, or about 0.12 inches... 2 significant digits, which is 'around' 0.10 inches.

[Pugilistic Animus]

I guess I should not ask questions from the Advanced British PPL:rolleyes:


for that example above my compass correction card says for hdg 090 fly 085 [radio on]

what hdg do I fly on the DG? so that my course and track are coincident?

[Sir George Cayley]

PA

Why are you posting answers to compass issues on a thread started about hydroplaning?

Just curious - as you where.

SGC

[Pugilistic Animus]

Sir George Cayley; it's because, I'm lost:}

[Pugilistic Animus]

The formula for hydroplanning speed [and the effects of slush on acceleration] was derived from a Convair 880 and a Boeing 707 from trials conducted in Florida's NASA Dryden research center conducted in August 1961

[how'd they get slush in August in Florida---I have no clue:confused:]

note there's no formula for slush effects but the syntax implies that I meant so; I meant the trials also studied the effects of slush were conducted,...:)

PA

[john_tullamarine]

Probably useful to review some of the work on this stuff ...

(a) Derivation of an empirical equation relating critical hydroplaning speed .... NASA (http://hdl.handle.net/2060/19920076041)

(b) Continued Research on Tire Hydroplaning .. NASA (http://hdl.handle.net/2060/19920075834)

(c) Phenomena of pneumatic tire hydroplaning (http://hdl.handle.net/2060/19640000612)

(d) this article has a picture of a sled test facility (http://oea.larc.nasa.gov/PAIS/Groove.html) and there are some video runs (http://www.nasaimages.org/luna/servlet/detail/NVA2~20~20~54093~125018:NASA-Connect---Crash---ALDF-Testing?qvq=q:hydroplaning;lc:nasaNAS~20~20,NVA2~14~14,NVA2~ 28~28,nasaNAS~4~4,nasaNAS~5~5,NVA2~8~8,NVA2~16~16,nasaNAS~22 ~22,nasaNAS~13~13,NVA2~20~20,NVA2~25~25,nasaNAS~6~6,NVA2~1~1 ,NVA2~9~9,NVA2~27~27,NVA2~18~18,NVA2~13~13,nasaNAS~10~10,NVA 2~22~22,nasaNAS~7~7,nasaNAS~8~8,nasaNAS~12~12,NVA2~29~29,NVA 2~24~24,NVA2~15~15,NVA2~4~4,nasaNAS~9~9,NSVS~3~3,nasaNAS~2~2 ,NVA2~17~17,NVA2~30~30,NVA2~21~21,NVA2~26~26,NVA2~23~23,nasa NAS~16~16,NVA2~19~19,NVA2~31~31,NVA2~32~32&mi=3&trs=5
) in this PR video from NASA.

(e) The other technique is to pond a narrow section of runway and run the tests on a single wheel assembly, typically the nose wheel. This, as I recall from seeing some footage years ago was the basis for the tests in the early 60s .. but I haven't been able to track down any video records. The technique is used also for engine water ingestion qualification trials. For info, this Airbus video (http://www.vidchili.com/video/8LPnnMDzwwK/A380_Aquaplaning_Hydroplaning_test/) gives you an idea of the technique.

(f) Spindown research clip (http://www.archive.org/details/NIX-LV-1998-00072)

There's plenty of other stuff around if you want to do some searches ...

(Checkboard cited (c) but it's such a basic report on the subject it's worth repeating here.)

[YRP]

A Hydroplane is a kind of speedboat. Did you by any chance mean to ask about "Aquaplaning"????

Hydroplane - Wikipedia, the free encyclopedia

Never mind. Accuracy has never been seen as particurlarly important on PPRuNe.


Amazing the new class of "intellectuals" we are getting out there who think an entry in a free encyclopedia, written by anyone who feels like it, is a supporting argument.


I wouldn't argue the point that quoting a freely editable encyclopedia to back an argument is pretty dubious...

But, to be fair to Wikipedia, the article quoted has immediately under the title:
"This article is about a specific type of motorboat. For other uses, see Hydroplaning."

:)