Re: Takeoff wheel spin

From:         hackett@southwind.net (Kim Hackett)
Organization: Your Organization
Date:         18 Sep 96 13:52:16 
References:   1 2 3
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In article <airliners.1996.1852@ohare.Chicago.COM>, Robert Moore
<bobmoore@wwd.net> says:
>
>Kim Hackett wrote:
>
>> There is no retardation of the wheel that I know of.
>> I think it is ok for them to be spinning when they
>> enter the wheel well.
>> I suppose the pilot could touch the brakes after
>> lift off to stop the wheels from spinning.
>
>Why in the world would someone with absolutely NO knowledge of the subject
>at hand want to post BS such as this.
>
>Having flown various Boeing and Lockheed jet transports for over 25 years,
>they ALL had a auto-brake system on the main gear and rub strips on the
>nose gear. Pilots were forbidden from using the regular brakes due to the
>possibility of breaking the tire/wheel seal.
>
>Sheeeesh!!  Save us from the Internet.

I do not believe that the original author of the newsgroup thread limited
his question of tire rotation to Boeing and Lockheed aircraft.  For this
reason it seems appropriate to also consider other jet aircraft.


Today I asked other engineers here at Cessna how the Cessna Citation jet
aircraft are designed with regard to tire rotation after takeoff.  I
learned the following:

1) Cessna does not use rub strips of any kind in the nose or main gear
wheel wells of any Citation jet aircraft.

2) The straight wing Citation jets; Model 500 (Citation 1), Model 525
(CitationJet), Model 550 (Citation 2), Model 560 (Citation 5), and Model
560XL (Citation Excel) do not have a method of stopping main tire rotation
using any kind of auto-braking system.  For these aircraft, the tire
rotation is not restricted in any way during or after main gear
retraction.

3) The swept wing Citations; Model 650 (Citation 3, 6, and 7) and the
Model 750 (Citation X) incorporate an auto-brake pressure pulse for the
main gear tires only and is tied to the gear retract switch.

4) The nose gears on Citation jets do not have brakes, therefore a nose
wheel auto-brake system is impossible.

5) According to our engineering flight test pilots, they routinely tap the
brakes after liftoff to stop the main tire rotation.  The tire/wheel seal
 problem that you mentioned does not seem to be a problem on our jets.

6) Our Citation jet Models 550 and above are certified to Airworthiness
Standard FAR 25 for Transport Category Airplanes.  This is the same FAA
certification basis as the Boeing and Lockheed aircraft that PanAm flew.
According to Cessnas FAA DER for Aircraft Loads, there is no FAR Part 25
requirement to eliminate tire rotation prior to gear retraction into the
wheel wells.  In fact, FAR 25 paragraph 25.729 Retracting Mechanisms
specifies that the landing gear retracting mechanism, wheel well doors,
and supporting structure must be designed to withstand the gyroscopic
loads resulting from the wheels rotating at a peripheral speed equal to
1.3 times Vs occurring at airspeeds up to 1.6 times Vs1.

In conclusion, every straight wing Citation jet that is flying in the
world today has no method to stopping tire rotation after takeoff.  In
addition, no Citation jets have a method of stopping nose tire rotation
after takeoff.  My statements in the newsgroup are correct for Citation
jet aircraft and is consistent with engineering flight test practices at
Cessna.


I totally agree with your conviction that those who do not know what they
are talking about should not obtrude ideas as fact, nor criticize the
views of those who know what they are talking about.


Kim Hackett
Engineering Group Leader, Aerodynamic Loads
Cessna Aircraft Company
Wichita, Kansas